During the Second World War, the three Axis powers of Germany, Italy, and Finland mobilized the largest share of their male population. For the Allies, the Soviet Union mobilized the largest share of men, as well as the largest total army of any country, but it was restricted in its ability to mobilize more due to the impact this would have on its economy. Other notable statistics come from the British Empire, where a larger share of men were drafted from Dominions than from the metropole, and there is also a discrepancy between the share of the black and white populations from South Africa.

However, it should be noted that there were many external factors from the war that influenced these figures. For example, gender ratios among the adult populations of many European countries was already skewed due to previous conflicts of the 20th century (namely WWI and the Russian Revolution), whereas the share of the male population eligible to fight in many Asian and African countries was lower than more demographically developed societies, as high child mortality rates meant that the average age of the population was much lower.

In 1800, the population of the region of present-day India was approximately 169 million. The population would grow gradually throughout the 19th century, rising to over 240 million by 1900. Population growth would begin to increase in the 1920s, as a result of falling mortality rates, due to improvements in health, sanitation and infrastructure. However, the population of India would see it’s largest rate of growth in the years following the country’s independence from the British Empire in 1948, where the population would rise from 358 million to over one billion by the turn of the century, making India the second country to pass the billion person milestone. While the rate of growth has slowed somewhat as India begins a demographics shift, the country’s population has continued to grow dramatically throughout the 21st century, and in 2020, India is estimated to have a population of just under 1.4 billion, well over a billion more people than one century previously. Today, approximately 18% of the Earth’s population lives in India, and it is estimated that India will overtake China to become the most populous country in the world within the next five years.

It is estimated that the Second World War was responsible for the deaths of approximately 3.76 percent of the world's population between 1939 and 1945. In 2022, where the world's population reached eight billion, this would be equal to the death of around 300 million people.

The region that experienced the largest loss of life relative to its population was the South Seas Mandate - these were former-German territories given to the Empire of Japan through the Treaty of Versailles following WWI, and they make up much of the present-day countries of the Marshall Islands, Micronesia, the Northern Mariana Islands (U.S. territory), and Palau. Due to the location and strategic importance of these islands, they were used by the Japanese as launching pads for their attacks on Pearl Harbor and in the South Pacific, while they were also taken as part of the Allies' island-hopping strategy in their counteroffensive against Japan. This came at a heavy cost for the local populations, a large share of whom were Japanese settlers who had moved there in the 1920s and 1930s. Exact figures for both pre-war populations and wartime losses fluctuate by source, however civilian losses in these islands were extremely high as the Japanese defenses resorted to more extreme measures in the war's final phase.

In 1800, the region of Germany was not a single, unified nation, but a collection of decentralized, independent states, bound together as part of the Holy Roman Empire. This empire was dissolved, however, in 1806, during the Revolutionary and Napoleonic eras in Europe, and the German Confederation was established in 1815. Napoleonic reforms led to the abolition of serfdom, extension of voting rights to property-owners, and an overall increase in living standards. The population grew throughout the remainder of the century, as improvements in sanitation and medicine (namely, mandatory vaccination policies) saw child mortality rates fall in later decades. As Germany industrialized and the economy grew, so too did the argument for nationhood; calls for pan-Germanism (the unification of all German-speaking lands) grew more popular among the lower classes in the mid-1800s, especially following the revolutions of 1948-49. In contrast, industrialization and poor harvests also saw high unemployment in rural regions, which led to waves of mass migration, particularly to the U.S.. In 1886, the Austro-Prussian War united northern Germany under a new Confederation, while the remaining German states (excluding Austria and Switzerland) joined following the Franco-Prussian War in 1871; this established the German Empire, under the Prussian leadership of Emperor Wilhelm I and Chancellor Otto von Bismarck. 1871 to 1945 - Unification to the Second World War The first decades of unification saw Germany rise to become one of Europe's strongest and most advanced nations, and challenge other world powers on an international scale, establishing colonies in Africa and the Pacific. These endeavors were cut short, however, when the Austro-Hungarian heir apparent was assassinated in Sarajevo; Germany promised a "blank check" of support for Austria's retaliation, who subsequently declared war on Serbia and set the First World War in motion. Viewed as the strongest of the Central Powers, Germany mobilized over 11 million men throughout the war, and its army fought in all theaters. As the war progressed, both the military and civilian populations grew increasingly weakened due to malnutrition, as Germany's resources became stretched. By the war's end in 1918, Germany suffered over 2 million civilian and military deaths due to conflict, and several hundred thousand more during the accompanying influenza pandemic. Mass displacement and the restructuring of Europe's borders through the Treaty of Versailles saw the population drop by several million more.

Reparations and economic mismanagement also financially crippled Germany and led to bitter indignation among many Germans in the interwar period; something that was exploited by Adolf Hitler on his rise to power. Reckless printing of money caused hyperinflation in 1923, when the currency became so worthless that basic items were priced at trillions of Marks; the introduction of the Rentenmark then stabilized the economy before the Great Depression of 1929 sent it back into dramatic decline. When Hitler became Chancellor of Germany in 1933, the Nazi government disregarded the Treaty of Versailles' restrictions and Germany rose once more to become an emerging superpower. Hitler's desire for territorial expansion into eastern Europe and the creation of an ethnically-homogenous German empire then led to the invasion of Poland in 1939, which is considered the beginning of the Second World War in Europe. Again, almost every aspect of German life contributed to the war effort, and more than 13 million men were mobilized. After six years of war, and over seven million German deaths, the Axis powers were defeated and Germany was divided into four zones administered by France, the Soviet Union, the UK, and the U.S.. Mass displacement, shifting borders, and the relocation of peoples based on ethnicity also greatly affected the population during this time. 1945 to 2020 - Partition and Reunification In the late 1940s, cold war tensions led to two distinct states emerging in Germany; the Soviet-controlled east became the communist German Democratic Republic (DDR), and the three western zones merged to form the democratic Federal Republic of Germany. Additionally, Berlin was split in a similar fashion, although its location deep inside DDR territory created series of problems and opportunities for the those on either side. Life quickly changed depending on which side of the border one lived. Within a decade, rapid economic recovery saw West Germany become western Europe's strongest economy and a key international player. In the east, living standards were much lower, although unemployment was almost non-existent; internationally, East Germany was the strongest economy in the Eastern Bloc (after the USSR), though it eventually fell behind the West by the 1970s. The restriction of movement between the two states also led to labor shortages in t...

Over the course of the Second World War approximately 127.2 million people were mobilized. The world's population in 1940 was roughly 2.3 billion, meaning that between five and six percent of the world was drafted into the military in some capacity. Approximately one in every 25 people mobilized were women, who generally served in an administrative or medical role, although hundreds of thousands of women did see active combat. Largest armies In absolute numbers, the Soviet Union mobilized the largest number of people at just under 34.5 million, and this included roughly 35 percent of the USSR's male population. By the war's end, more Soviets were mobilized than all European Axis powers combined. However, in relative terms, it was Germany who mobilized the largest share of its male population, with approximately 42 percent of men serving. The USSR was forced to find a balance between reinforcing its frontlines and maintaining agricultural and military production to supply its army (in addition to those in annexed territory after 1941), whereas a large share of soldiers taken from the German workforce were replaced by workers drafted or forcibly taken from other countries (including concentration camp prisoners and PoWs). Studying the figures The figures given in these statistics are a very simplified and rounded overview - in reality, there were many nuances in the number of people who were effectively mobilized for each country, their roles, and their status as auxiliary, collaborative, or resistance forces. The British Empire is the only power where distinctions are made between the metropole and its colonies or territories, whereas breakdowns of those who fought in other parts of Asia or Africa remains unclear. Additionally, when comparing this data with total fatalities, it is important to account for the civilian death toll, i.e. those who were not mobilized.

The island of Ireland is split into 32 different counties, and from 1800 until 1921 the whole island was a part of the United Kingdome of Great Britain and Ireland (although Britain had been a controlling presence on the island for considerably longer than this). In 1921 the island was split into two separate states, where the six counties with the highest population of Protestants formed part of the United Kingdom of Great Britain and Northern Ireland, and the other 26 counties became the Independent Republic of Ireland. From 1821 until 1841, the population of these 26 counties was growing steadily, until the Great Famine from 1845 to 1849 swept across the island, particularly devastating the west and south.

The famine was caused by a Europe-wide potato blight that contributed to mass starvation and death throughout the continent, although it's impact on Ireland was much harsher than anywhere else. The potato blight affected Ireland so severely as the majority of potatoes in Ireland were of a single variety which allowed the disease to spread much faster than in other countries. People in the west and south of Ireland were particularly dependent on potatoes, and these areas were affected more heavily than the north and west, where flax and cereals were the staple. As the potato blight spread, the population became increasingly reliant on dairy and grain products, however a lot of these resources were relocated by the British military to combat food shortages in Britain. Due to disproportional dependency on potatoes, and mismanagement by the British government, over one million people died and a further one million emigrated. The Great Famine lasted from just 1845 to 1849, but it's legacy caused almost a century of population decline, and to this day, the population of Ireland has never exceeded it's pre-famine levels.

The population decline continued well into the twentieth century, during which time the Republic of Ireland achieved independence from the British Empire. After centuries of fighting and rebellion against British rule, Irish nationalists finally gained some independence from Britain in 1921, establishing an Irish Republic in the 26 counties. There was a lot of conflict in Ireland in the early 1900s, through the War of Independence and Irish Civil War, however the population of the Republic began growing again from the 1960s onwards as the quality of life improved and the emigration rate declined. The population was at it's lowest from 1926 to 1971, where it remained at just under three million, but in the following fifty years the population has grown by over two million people.

During the eighteenth century, it is estimated that France's population grew by roughly fifty percent, from 19.7 million in 1700, to 29 million by 1800. In France itself, the 1700s are remembered for the end of King Louis XIV's reign in 1715, the Age of Enlightenment, and the French Revolution. During this century, the scientific and ideological advances made in France and across Europe challenged the leadership structures of the time, and questioned the relationship between monarchial, religious and political institutions and their subjects. France was arguably the most powerful nation in the world in these early years, with the second largest population in Europe (after Russia); however, this century was defined by a number of costly, large-scale conflicts across Europe and in the new North American theater, which saw the loss of most overseas territories (particularly in North America) and almost bankrupted the French crown. A combination of regressive taxation, food shortages and enlightenment ideologies ultimately culminated in the French Revolution in 1789, which brought an end to the Ancien Régime, and set in motion a period of self-actualization.

War and peace

After a volatile and tumultuous decade, in which tens of thousands were executed by the state (most infamously: guillotined), relative stability was restored within France as Napoleon Bonaparte seized power in 1799, and the policies of the revolution became enforced. Beyond France's borders, the country was involved in a series of large scale wars for two almost decades, and the First French Empire eventually covered half of Europe by 1812. In 1815, Napoleon was defeated outright, the empire was dissolved, and the monarchy was restored to France; nonetheless, a large number of revolutionary and Napoleonic reforms remained in effect afterwards, and the ideas had a long-term impact across the globe. France experienced a century of comparative peace in the aftermath of the Napoleonic Wars; there were some notable uprisings and conflicts, and the monarchy was abolished yet again, but nothing on the scale of what had preceded or what was to follow. A new overseas colonial empire was also established in the late 1800s, particularly across Africa and Southeast Asia. Through most of the eighteenth and nineteenth century, France had the second largest population in Europe (after Russia), however political instability and the economic prioritization of Paris meant that the entire country did not urbanize or industrialize at the same rate as the other European powers. Because of this, Germany and Britain entered the twentieth century with larger populations, and other regions, such as Austria or Belgium, had overtaken France in terms of industrialization; the German annexation of Alsace-Lorraine in the Franco-Prussian War was also a major contributor to this.

World Wars and contemporary France

Coming into the 1900s, France had a population of approximately forty million people (officially 38 million* due to to territorial changes), and there was relatively little growth in the first half of the century. France was comparatively unprepared for a large scale war, however it became one of the most active theaters of the First World War when Germany invaded via Belgium in 1914, with the ability to mobilize over eight million men. By the war's end in 1918, France had lost almost 1.4 million in the conflict, and approximately 300,000 in the Spanish Flu pandemic that followed. Germany invaded France again during the Second World War, and occupied the country from 1940, until the Allied counter-invasion liberated the country during the summer of 1944. France lost around 600,000 people in the course of the war, over half of which were civilians. Following the war's end, the country experienced a baby boom, and the population grew by approximately twenty million people in the next fifty years (compared to just one million in the previous fifty years). Since the 1950s, France's economy quickly grew to be one of the strongest in the world, despite losing the vast majority of its overseas colonial empire by the 1970s. A wave of migration, especially from these former colonies, has greatly contributed to the growth and diversity of France's population today, which stands at over 65 million people in 2020.

In 1800, the population of the area of modern-day Pakistan was estimated to be just over 13 million. Population growth in the 19th century would be gradual in the region, rising to just 19 million at the turn of the century. In the early 1800s, the British Empire slowly consolidated power in the region, eventually controlling the region of Pakistan from the mid-19th century onwards, as part of the British Raj. From the 1930s on, the population's growth rate would increase as improvements in healthcare (particularly vaccination) and sanitation would lead to lower infant mortality rates and higher life expectancy. Independence In 1947, the Muslim-majority country of Pakistan gained independence from Britain, and split from the Hindu-majority country of India. In the next few years, upwards of ten million people migrated between the two nations, during a period that was blemished by widespread atrocities on both sides. Throughout this time, the region of Bangladesh was also a part Pakistan (as it also had a Muslim majority), known as East Pakistan; internal disputes between the two regions were persistent for over two decades, until 1971, when a short but bloody civil war resulted in Bangladesh's independence. Political disputes between Pakistan and India also created tension in the first few decades of independence, even boiling over into some relatively small-scale conflicts, although there was some economic progress and improvements in quality of life for Pakistan's citizens. The late 20th century was also characterized by several attempts to become democratic, but with intermittent periods of military rule. Between independence and the end of the century, Pakistan's population had grown more than four times in total. Pakistan today Since 2008, Pakistan has been a functioning democracy, with an emerging economy and increasing international prominence. Despite the emergence of a successful middle-class, this is prosperity is not reflected in all areas of the population as almost a quarter still live in poverty, and Pakistan ranks in the bottom 20% of countries according to the Human Development Index. In 2020, Pakistan is thought to have a total population of over 220 million people, making it the fifth-most populous country in the world.

Humans have been living on the continent of Australia (name derived from "Terra Australis"; Latin for "the southern land") for approximately 65,000 years, however population growth was relatively slow until the nineteenth century. Europeans had made some contact with Australia as early as 1606, however there was no significant attempt at settlement until the late eighteenth century. By 1800, the population of Australia was approximately 350,000 people, and the majority of these were Indigenous Australians. As colonization progressed the number of ethnic Europeans increased while the Australian Aboriginal population was decimated through conflict, smallpox and other diseases, with some communities being exterminated completely, such as Aboriginal Tasmanians. Mass migration from Britain and China After the loss of its American colonies in the 1780s, the British Empire looked to other parts of the globe to expand its sphere of influence. In Australia, the first colonies were established in Sydney, Tasmania and Western Australia. Many of these were penal colonies which became home to approximately 164,000 British and Irish convicts who were transported to Australia between 1788 and 1868. As the decades progressed, expansion into the interior intensified, and the entire country was claimed by Britain in 1826. Inland colonization led to further conflict between European settlers and indigenous Australians, which cost the lives of thousands of natives. Inward expansion also saw the discovery of many natural resources, and most notably led to the gold rushes of the 1850s, which attracted substantial numbers of Chinese migrants to Australia. This mass migration from non-European countries eventually led to some restrictive policies being introduced, culminating with the White Australia Policy of 1901, which cemented ethnic-European dominance in Australian politics and society. These policies were not retracted until the second half of the 1900s. Independent Australia Australia changed its status to a British dominion in 1901, and eventually became independent in 1931. Despite this, Australia has remained a part of the British Commonwealth, and Australian forces (ANZAC) fought with the British and their Allies in both World Wars, and were instrumental in campaigns such as Gallipoli in WWI, and the South West Pacific Theater in WWII. The aftermath of both wars had a significant impact on the Australian population, with approximately 90 thousand deaths in both world wars combined, as well as 15 thousand deaths as a result of the Spanish flu pandemic following WWI, although Australia experienced a significant baby boom following the Second World War. In the past fifty years, Australia has promoted immigration from all over the world, and now has one of the strongest economies and highest living standards in the world, with a population that has grown to over 25 million people in 2020.

From 1800 until the late twentieth century, there was a steady increase in Afghanistan's population. Throughout the nineteenth century, Afghanistan became a battleground for the British Empire, who tried to control the area in order to prevent Russian expansion towards the British Raj. Despite resisting the British invasion in the first Anglo-Afghan War, (where the British Army was almost completely wiped out), the Second Anglo-Afghan War in 1880 saw Britain seize control of the region. In contrast to the neighboring colonies on the Indian subcontinent, Britain did not colonize Afghanistan for economic purposes, therefore they did not invest in agriculture or infrastructure, nor introduce medicine in the same way they did in the Raj, and focused only on Afghanistan's international affairs. Independence and progress The Third Anglo-Afghan War, where Afghan forces invaded British India in 1919, resulted in Afghanistan's independence finally being declared after two months of conflict. The next decade saw some major reforms that attempted to modernize Afghan society, (notable progress was made for women's rights and education) however this alienated many conservative and religious tribes, and a civil war broke out in 1928. After the war (and brief usurpation) the new King of Afghanistan, Nadir Khan, consolidated power, and also moved to modernize the country, but more gradually than his predecessors in order to avoid further alienation and conflict. Khan's approach remained in place until the 1970s, when a bloodless coup established a republic. The republic never achieved political stability, and the Sauri Revolution of 1978 resulted in the formation of the communist Democratic Republic of Afghanistan. Continuous war Despite some progressive reforms, such as banning forced marriages and opening a space for women in politics, the determination to promote state atheism combined with the country's economic dependence on the Soviet Union led to serious opposition from Afghan people, particularly in rural areas. On December 24, 1979, the Soviet Union (backed by the Afghan government) invaded the country, and the ensuing decade-long guerilla war resulted in as many as two million fatalities and three million wounded, as well as two million internally displaced persons and five million refugees abroad. Soviet withdrawal was seen as a western victory, as they had supported the Taliban in their fight against the Soviets, however a decade later the Taliban refused to hand over Osama Bin Laden and other al-Qaeda suspects to the US, following the 9/11 attacks in 2001. This led to US and British forces launching Operation Enduring Freedom in October 2001, and an intensive bombing campaign followed, destroying many major cities in the country. The Taliban government was toppled in December 2001, and in 2002 a western-led rebuilding of the country began. Over the past two decades, many displaced Afghans have returned home, leading to some economic growth, however guerilla fighting continues and there is a strong military presence in the country (including many Taliban controlled areas). In 2020, Afghanistan remains one of the poorest and most politically unstable countries in the world, however the rapid population growth experienced in recent decades is expected to continue well into the future, as improvements in medical care and humanitarian aid become more widespread across the country.

The fertility rate of a country is the average number of children that women from that country would have throughout their reproductive years. In the United Kingdom in 1800, the average woman of childbearing age would have five children over the course of their lifetime. Over the next 35 years the fertility rate was quite sporadic, rising to over 5.5 in the 1810s and 1820s, then dropping to 4.9 by 1835. This was during and after the Napoleonic Wars and the War of 1812 with the US, which was a time of increased industrialization, economic depression and high unemployment after the war. As things became more stable, and the 'Pax Britannica' (a period of relative, international peace and economic prosperity for the British Empire) came into full effect, the fertility rate plateaued until 1880, before dropping gradually until the First World War. The fertility rate then jumped from 2.6 to 3.1 children per woman between 1915 and 1920, as many men returned from the war. It then resumed it's previous trajectory in the interwar years, before increasing yet again after the war (albeit, for a much longer time than after WWI), in what is known as the 'Baby Boom'. Like the US, the Baby Boom lasted until around 1980, where it then fell to 1.7 children per woman, and it has remained around this number (between 1.66 and 1.87) since then.

After the Second World War, the deadliest conflict for the British Armed Forces was the Malayan Emergency, which lasted from 1948 to 1960 and resulted in the deaths of 1,442 British soldiers. Over a much longer time period, between 1968 and 2007, there were 1,441 operational deaths for the British Armed Forces in Northern Ireland. The Korean War was a noticeably deadly conflict despite its relatively short duration, and had the third-highest number of fatalities for British troops at 1,129. The wars of decolonization The rapid disintegration of the British Empire after 1945 is the cause of many of the conflicts displayed here. In the aftermath of World War Two, there were 70 modern-day countries in the British Empire, but by 1997, Britain’s colonial Empire had vanished. The Palestinian Emergency, which after 1945 caused 754,000 British casualties, as well as the aforementioned Malayan Emergency are just some examples of Britain’s disorderly withdrawal from regions it once controlled. Although the UK won the Falklands War in 1982, the UK's armed forces suffered 237 operational deaths in the ten-day conflict. Recent conflicts The UK armed forces have been involved in several more recent military conflicts, and the deadliest of these was by far the War in Afghanistan, which was responsible for 457 British fatalities. The UK’s involvement in the fight against ISIS in Iraq and Syria is also ongoing, although unlike the Iraq War that took place between 2003 and 2011, where the UK suffered 178 operational deaths, the conflict is fought primarily by the air force. Although no UK soldiers are fighting the War in Ukraine, the UK government has provided extensive equipment and training to the Ukrainian armed forces since 2022, along with several other western nations.  

In 2025, there were around 137,000 regular personnel serving in the British Armed Forces, compared with 138,000 in the previous year. In the first half of the twentieth century, there were two huge spikes in the number of active personnel which represented the final years of World War One and World War Two, numbering 4.58 million and 4.69 million in 1918 and 1945 respectively. Ever since 1945, the size of the regular armed forces has been in almost constant decline, with the noticeable exception of the early 1950s, when the number of active personnel increased by almost 200,000 because of the Korean War. The winds of change There are several reasons why the number of personnel in Britain’s armed forces has declined. Britain is involved in a far fewer conventional military conflicts today than it was in the past. As the size of Britain’s empire declined rapidly after 1945, so too did the UK's global military commitments. There are also more recent developments, such as the UK government’s Strategic Defence and Security Review of 2010, which outlined personnel would be cut throughout the 2010s to modernize the UK’s armed forces. Recent geopolitical events such as the War in Ukraine have, however, led to commitments from the UK government to spend more on defence, and eventually even a reversal of personnel cuts. Branches of the UK military There are three main branches of the UK armed forces, the British Army, the Royal Navy, the Royal Air Force, and the Royal Marines. Of the 181,000 people serving in the UK’s armed forces in 2025, over half of them were in the British Army, which had around 109,000 personnel. The next largest branch was the Royal Navy at 37,900, followed by the RAF at 34,800 personnel. The average age for people serving in the armed forces was 31 in 2024, with the Royal Air Force having a slightly higher average age group than the other branches, at 33.

Before the Second World War, the Soviet Union was the largest individual world power in terms of territory, at over 21 million square kilometers. When the territories of the United Kingdom it's colonies and dominions are combined, then the expanse of the British Empire totaled at almost 35 million square kilometers, making it larger than the USSR.

The Axis Powers, led by Germany, Italy, and Japan, controlled a much smaller share of the globe than the Allied Powers in 1938 - however, by 1941, the majority of Europe was under (German-led) Axis control, while Japan had taken much of the Western territories in Asia and had pushed further into China. Italy had also sought to consolidate its power in North and East Africa at this time, but was largely contained by British Commonwealth Forces. Although 1941 and 1942 marked the largest territorial gains for the Axis Powers in Europe and Asia, Italy had lost virtually all of its African colonies by the end of 1942, which totaled at just under 3.5 million square kilometers of land. Late 1942 also marked the turning point in the war in the other theaters, where the Soviet counteroffensive started pushing the German lines back in Europe, while American and Commonwealth Forces began pushing the Japanese north through the Asia-Pacific at the end of the year. The war in Europe ended in May, 1945, and in the Pacific in September, 1945.

Prior to 1829, the area of modern day Greece was largely under the control of the Ottoman Empire. In 1821, the Greeks declared their independence from the Ottomans, and achieved it within 8 years through the Greek War of Independence. The Independent Kingdom of Greece was established in 1829 and made up the southern half of present-day, mainland Greece, along with some Mediterranean islands. Over the next century, Greece's borders would expand and readjust drastically, through a number of conflicts and diplomatic agreements; therefore the population of Greece within those political borders** was much lower than the population in what would be today's borders. As there were large communities of ethnic Greeks living in neighboring countries during this time, particularly in Turkey, and the data presented here does not show the full extent of the First World War, Spanish Flu Pandemic and Greko-Turkish War on these Greek populations. While it is difficult to separate the fatalities from each of these events, it is estimated that between 500,000 and 900,000 ethnic Greeks died at the hands of the Ottomans between the years 1914 and 1923, and approximately 150,000 died due to the 1918 flu pandemic. These years also saw the exchange of up to one million Orthodox Christians from Turkey to Greece, and several hundred thousand Muslims from Greece to Turkey; this exchange is one reason why Greece's total population did not change drastically, despite the genocide, displacement and demographic upheaval of the 1910s and 1920s. Greece in WWII A new Hellenic Republic was established in 1924, which saw a decade of peace and modernization in Greece, however this was short lived. The Greek monarchy was reintroduced in 1935, and the prime minister, Ioannis Metaxas, headed a totalitarian government that remained in place until the Second World War. Metaxas tried to maintain Greek neutrality as the war began, however Italy's invasion of the Balkans made this impossible, and the Italian army tried invading Greece via Albania in 1940. The outnumbered and lesser-equipped Greek forces were able to hold off the Italian invasion and then push them backwards into Albania, marking the first Allied victory in the war. Following a series of Italian failures, Greece was eventually overrun when Hitler launched a German and Bulgarian invasion in April 1941, taking Athens within three weeks. Germany's involvement in Greece meant that Hitler's planned invasion of the Soviet Union was delayed, and Hitler cited this as the reason for it's failure (although most historians disagree with this). Over the course of the war approximately eight to eleven percent of the Greek population died due to fighting, extermination, starvation and disease; including over eighty percent of Greece's Jewish population in the Holocaust. Following the liberation of Greece in 1944, the country was then plunged into a civil war (the first major conflict of the Cold War), which lasted until 1949, and saw the British and American-supported government fight with Greek communists for control of the country. The government eventually defeated the Soviet-supported communist forces, and established American influence in the Aegean and Balkans throughout the Cold War. Post-war Greece From the 1950s until the 1970s, the Marshall Plan, industrialization and an emerging Tourism sector helped the Greek economy to boom, with one of the strongest growth rates in the world. Apart from the military coup, which ruled from 1967 to 1974, Greece remained relatively peaceful, prosperous and stable throughout the second half of the twentieth century. The population reached 11.2 million in the early 2000s, before going into decline for the past fifteen years. This decline came about due to a negative net migration rate and slowing birth rate, ultimately facilitated by the global financial crisis of 2007 and 2008; many Greeks left the country in search of work elsewhere, and the economic troubles have impacted the financial incentives that were previously available for families with many children. While the financial crisis was a global event, Greece was arguably the hardest-hit nation during the crisis, and suffered the longest recession of any advanced economy. The financial crisis has had a consequential impact on the Greek population, which has dropped by 800,000 in 15 years, and the average age has increased significantly, as thousands of young people migrate in search of employment.

In 1800, the population of the island of Sri Lanka was approximately 1.2 million. This figure would begin to grow following the island’s complete annexation into the British Empire with the end of the Second Kandyan War in 1815. Population growth then increased much faster towards the end of the 19th century, as child mortality rates dropped and large numbers of Indian migrants were imported to work on British plantations. These migrants were largely Tamil migrants from southern India, and by 1911, this group would make up almost 13 percent of the island’s population (on top of the existing 13 percent Sri Lankan Tamil population).

Population growth would expand rapidly in the years immediately following the island’s independence from the British Empire in 1948. However, this growth would slow in the 1950s, as legislation passed by the Sinhalese-dominated government immediately following independence resulted in the removal of citizenship for an estimated 700,000 Indian Tamils, and the deportation of over 300,000 to India over the following three decades. Growth would slow even further after the ethnic clashes of Black July in 1983, which marked the beginning of a civil war in Sri Lanka which would last from 1983 to 2009 and result in the death of over 80,000 people, and the displacement of an estimated 800,000. However, since the end of the civil war in 2009, the population of Sri Lanka has continued to grow, and in 2020, the population of Sri Lanka is estimated to be over 21 million.

Much of Argentina's modern society and culture is rooted in the Spanish Empire's colonization of the region in the 16th century, along with the influx of European migration to the country around the turn of the twentieth century. There are records of human presence in the region dating back to the paleolithic period (3.3 million to 9,650 BCE) and the Incan Empire is known to have extended into the region before Columbus' arrival in the Americas in 1492; however most of this culture and civilization was wiped out by Europeans in the 1500s. During Spanish colonization, the majority of Argentina was a part of the Viceroyalty of the Río de la Plata (which also included territories in modern-day Chile, Bolivia, Paraguay and Uruguay) and was still economically bound to the Spanish crown. With a population of just 0.5 million in 1800, a combination of mass migration (particularly from Southern Europe) and high birth rates have helped Argentina's population grow above 45 million over the past two centuries.

Independence, Immigration and the Gold rush The age of enlightenment and revolutions in Europe inspired a longing in the region for independence, and Napoleon's invasion of Spain in 1808 was the catalyst for the Spanish Empire's downfall in the Americas, with Argentinian independence declared in 1816. The Spanish military was then defeated in mid 1800s, but for the majority of the next century there was little political or economic stability in the region, with several small-scale civil wars between the different Argentinian states. Starting with the government of Julio Argentino Roca in 1880, ten consecutive federal governments actively pursued a liberal economic policy which led to a massive wave of state-promoted European immigration; so much so that the number of migrants received by Argentina in that period was second only to the United States worldwide. This immigration led to the rejuvenation and reinvention of Argentinian society and economy to such an extent, that by 1908 the country had the seventh largest economy in the world. This in turn led to further immigration and higher standards of living. It is also worth noting that the Tierra del Fuego gold rush that started around 1883 and lasted to around 1906 also contributed greatly to immigration. Unfortunately, Argentina was unable to retain it's acquired economic might; it failed to develop industrially at the same speed as the rest of the world, and the Great Depression of 1929 set in motion an economic decline that contributed to much civil and political unrest.

The impact of Perón, and modern Argentina
The election of Juan Perón in 1946 proved to be a defining point in Argentina's history; Perón was a demagogue who imprisoned (and reportedly tortured) his rivals and critics, and whose isolationist policies and radical spending contributed to severe inflation. With the death of Perón's extremely popular wife, Eva Duarte, in 1952, his popularity declined and he was eventually exiled following a coup in 1955. Despite this exile, Perón returned in 1973 and re-assumed the presidency, until his death in 1974, where he was the succeeded by his third wife. Peron's political philosophy, known as "Peronism", is a mixture of right wing nationalist and left wing populist theories; although Peronism has developed greatly over time, its core belief system is the foundation of Argentina's largest party, the Justicialist Party (although they have become increasingly left wing since the Kirchner administrations).

With the expulsion of Perón in 1955, Argentina's trend of military coups and failed governments continued, and the country faced further economic instability. Despite all of this, medical advancements and improvements to quality of life across the globe helped Argentina's mortality rate to decline, and the population grew at a faster rate than ever before. In April 1982, Argentine forces invaded the British territory of the Falkland Islands, leading to a ten week war between the nations, that ended with Argentina's surrender in June. The war had a relatively small death toll, but contributed to riots in Buenos Aires, which helped to topple the military dictatorship and established the current democratic system. Following a severe recession that began in 2001, President Néstor Kirchner assumed office in 2003, and his wife took over from 2007 to 2015; during the Kirchner administrations, more than eleven million people were lifted out of poverty, and Argentina's economy grew in stature to become one of the Group of Twenty.

Throughout the early 20th century, China, India, and Japan were the three largest coal producers in Asia. Japan had the highest output in all years before the Second World War, and Japan's invasions of China in the 1930s was partly due to its desire to gain access to China's coal resources (there is an observable drop in China's output following the 1937 invasion).

India, on the other hand, was a part of the British Empire during this period, and coal production went largely uninterrupted by the war. Unlike many other European colonies or Indian industries, much of India's coal industry was in the hands of Indian owners, which supplied both international markets and domestic development, and contributed to the growth of the Indian upper classes.

In 1800, the population of Yemen was just under 2.6 million, and would gradually grow to just 3.2 million by the end of the 18th century. Between the mid-1800s and early-1900s, the north and south regions of present-day Yemen had been split into territories of the British and Ottoman empires respectively; the north became independent in 1918, during Ottoman dissolution, while the British did not withdraw from the region until 1967. Yemen would experience an exponential growth in population in the years beginning in the 1970s, following the discovery of petroleum in the country, though this would slow somewhat in the 1990s, in part the result of food shortages and instability throughout the country years following the unification of South Yemen and the Yemen Arab Republic. In 2020, the population of Yemen is estimated to be just under thirty million people, however, the country has been experiencing a civil war in since 2015, which has resulted in one of the most severe humanitarian crises in recent history, with over 100,000 deaths (mostly children, due to famine) as well as the displacement of millions of people, and one of the most severe cholera outbreaks in recent decades.

In 1938, the year before the Second World War, the United States had, by far, the largest economy in the world in terms of gross domestic product (GDP). The five Allied Great Powers that emerged victorious from the war, along with the three Axis Tripartite Pact countries that were ultimately defeated made up the eight largest independent economies in 1938.

When values are converted into 1990 international dollars, the U.S. GDP was over 800 billion dollars in 1938, which was more than double that of the second largest economy, the Soviet Union. Even the combined economies of the UK, its dominions, and colonies had a value of just over 680 billion 1990 dollars, showing that the United States had established itself as the world's leading economy during the interwar period (despite the Great Depression).

Interestingly, the British and Dutch colonies had larger combined GDPs than their respective metropoles, which was a key motivator for the Japanese invasion of these territories in East Asia during the war. Trade with neutral and non-belligerent countries also contributed greatly to the economic development of Allied and Axis powers throughout the war; for example, natural resources from Latin America were essential to the American war effort, while German manufacturing was often dependent on Swedish iron supplies.