The Second World War had a sever impact on gender ratios across European countries, particularly in the Soviet Union. While the United States had a balanced gender ratio of one man for every woman, in the Soviet Union the ratio was below 5:4 in favor of women, and in Soviet Russia this figure was closer to 4:3.

As young men were disproportionately killed during the war, this had long-term implications for demographic development, where the generation who would have typically started families in the 1940s was severely depleted in many countries.

The Second World War had a profound impact on gender ratios within the Soviet Union's population, and its effect on different age groups varied greatly. The Soviet population structure had already been shaped heavily by the First World War, the Russian Revolution, and the famines of the early 1920s and early 1930s. The impact of these events on mortality and fertility meant that, in 1941, the generations whose births corresponded with these events had a lower population than would be expected on a typical population model. For example, in 1941, those aged between 5 and 9 had a significantly lower population than those aged 10 to 14, due to the effects of the Soviet famine of 1932-1933. Additionally, women outnumbered men in all age groups except the very youngest, due to the disproportionate effect of conflict and infant mortality on male populations. Impact of WWII In order to observe the impact of the war, one must compare populations of specific age groups in 1941 with the following age group in 1946. For men of "fighting age" in 1941, i.e. those aged between 15 and 44, these populations experience the most substantial decrease over the course of the war. For example, there are 5.6 million men aged 15-19 in 1941, but just 3.5 million aged 20-24 in 1946, giving a decrease of 38 percent. This decrease of almost forty percent can be observed until the 45-49 group, where the difference is 25 percent. Additionally, women aged between 15 and 34 saw a disproportionate decrease in their populations over this period, as many enlisted in the army and took an active part in the conflict, most notably as medics, snipers, and pilots.

The war's impact on fertility and child mortality meant that, in 1946, the total population under four years old was less than half its size in 1941. Generally, variations between age groups then fluctuated in line with pre-war patterns, however the overall ratio of women to men increased further after the war. For all age groups over 20 years, the number of men decreased between these years, whereas all women's age groups over 30 years saw an increase; this meant that, despite the war, women over 30 had a higher life expectancy in 1946.

The Second World War severely altered the demographic composition of many countries, particularly in terms of gender ratios across certain age groups. For age groups below 14 years, there is little observable impact of the war on gender ratios, however, some countries see a drastic change across older generations, particularly in the Soviet Union. For men in their twenties (i.e. those in their late-teens or early-twenties when the war began), the ratio drops from 98 men per 100 women in the 15-19 age group, to 68 men per 100 women in the 25-29 group.

In addition to the Second World War, these figures are affected by trends in nature and other historical events. For example, women tend to have higher overall life expectancies than men, which typically sees gender ratios widen among older generations. The impact of the First World War is also most-observable in France's gender ratios for those aged in their fifties. Additionally, the gap in ratios remains high for the Soviet Union across older age groups due to the impact of the First World War and the famine of the early 1930s, however the figures for Russia itself are even lower as it was disproportionately affected by the Russian Revolution and famine of the 1920s.

In 1950, there were ** men per 100 women in Soviet Union republics. As a consequence of the World War II, referred to as the Great Patriotic War in Russia, the male-to-female ratio was significantly lower in age groups older than 25 years.

In all age groups until 29 years old, there were more men than women in Russia as of January 1, 2024. After that age, the female population outnumbered the male population in each category. The most represented age group in the country was from 35 to 39 years old, with approximately *** million women and *** million men. Male-to-female ratio in Russia The number of men in Russia was historically lower than the number of women, which was a result of population losses during World War I and World War II. In 1950, in the age category from 25 to 29 years, ** men were recorded per 100 women in the Soviet Union. In today’s Russia, the female-to-male ratio in the same age group reached *** women per 1,000 men. Russia has the highest life expectancy gender gap The World Health Organization estimated the average life expectancy of women across the world at over five years longer than men. In Russia, this gap between genders exceeded 10 years. According to the study “Burden of disease in Russia, 1980-2016: A systematic analysis for the Global Burden of Disease Study 2016,” Russia had the highest gender difference in life expectancy worldwide.

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.

The Second World War's Eastern Front, the largest theater of war in history, was largely dominated by the conflict between Germany and the Soviet Union. The two countries had agreed upon an unexpected peace pact in 1939, with the joint invasion and partition of Poland, but this peace was broken in June 1941 when Germany invaded the Soviet Union during Operation Barbarossa. Germany's economic and technological superiority, alongside its Blitzkrieg military strategy, allowed it to gain the upper hand in the early stages of the conflict. Within six months the Germans had pushed the frontlines back to Moscow, and almost 40 percent of the Soviet population now lived in occupied territory. German gains at the expense of the Soviets was reflected in the changing balance of their economies - Germany's GDP grew each year until 1944, whereas the Soviet GDP fell by one third between 1940 and 1942.

Differences in army sizes and military manpower of nations played a crucial role in the Second World War. While the Allied nations and their colonies or dominions had significantly larger combined populations than the Axis powers, the difference in the number of service personnel at their disposal was much smaller, especially in the war's early phase. Eastern Front With the annexation of Poland, Czechoslovakia, and the Balkans by mid-1941, the Axis forces in the Eastern theater outnumbered the Soviet Union. Following the launch of Operation Barbarossa in June 1941, the Axis forces were then able to push the Soviets as far back as Moscow - when the frontline stabilized, the Soviet Union was able to call upon its larger population to replenish and reinforce its ranks, eventually outnumbering the enemy the following year. Many Soviet women were also drafted in to fight, with notable and decorated examples serving as snipers, pilots, and artillery operators. Western Allies The combined Allied forces in the Pacific and on the Western European fronts (i.e. those mostly led by the UK and U.S.) always outnumbered the Axis powers. This was largely due to the increased mobilization of the United States military after 1941, particularly in the build up to the Invasion of Normandy on June 6, 1944, as well as the redistribution of Germany's forces from the Eastern to Western fronts in response to this, and the withdrawal of Italy from the war in late 1943. Japan did ramp up its conscription efforts in the final years of the war, but it was not enough to offset the huge numerical advantage of the Allies.

Estimates for the total death count of the Second World War generally range somewhere between 70 and 85 million people. The Soviet Union suffered the highest number of fatalities of any single nation, with estimates mostly falling between 22 and 27 million deaths. China then suffered the second greatest, at around 20 million, although these figures are less certain and often overlap with the Chinese Civil War. Over 80 percent of all deaths were of those from Allied countries, and the majority of these were civilians. In contrast, 15 to 20 percent were among the Axis powers, and the majority of these were military deaths, as shown in the death ratios of Germany and Japan. Civilian deaths and atrocities It is believed that 60 to 67 percent of all deaths were civilian fatalities, largely resulting from war-related famine or disease, and war crimes or atrocities. Systematic genocide, extermination campaigns, and forced labor, particularly by the Germans, Japanese, and Soviets, led to the deaths of millions. In this regard, Nazi activities alone resulted in 17 million deaths, including six million Jews in what is now known as The Holocaust. Not only was the scale of the conflict larger than any that had come before, but the nature of and reasoning behind this loss make the Second World War stand out as one of the most devastating and cruelest conflicts in history. Problems with these statistics Although the war is considered by many to be the defining event of the 20th century, exact figures for death tolls have proven impossible to determine, for a variety of reasons. Countries such as the U.S. have fairly consistent estimates due to preserved military records and comparatively few civilian casualties, although figures still vary by source. For most of Europe, records are less accurate. Border fluctuations and the upheaval of the interwar period mean that pre-war records were already poor or non-existent for many regions. The rapid and chaotic nature of the war then meant that deaths could not be accurately recorded at the time, and mass displacement or forced relocation resulted in the deaths of many civilians outside of their homeland, which makes country-specific figures more difficult to find. Early estimates of the war’s fatalities were also taken at face value and formed the basis of many historical works; these were often very inaccurate, but the validity of the source means that the figures continue to be cited today, despite contrary evidence.

In comparison to Europe, estimate ranges are often greater across Asia, where populations were larger but pre-war data was in short supply. Many of the Asian countries with high death tolls were European colonies, and the actions of authorities in the metropoles, such as the diversion of resources from Asia to Europe, led to millions of deaths through famine and disease. Additionally, over one million African soldiers were drafted into Europe’s armies during the war, yet individual statistics are unavailable for most of these colonies or successor states (notably Algeria and Libya). Thousands of Asian and African military deaths went unrecorded or are included with European or Japanese figures, and there are no reliable figures for deaths of millions from countries across North Africa or East Asia. Additionally, many concentration camp records were destroyed, and such records in Africa and Asia were even sparser than in Europe. While the Second World War is one of the most studied academic topics of the past century, it is unlikely that we will ever have a clear number for the lives lost in the conflict.