World War II was the deadliest and most destructive conflict in human history. Beginning with Germany’s invasion of Poland in September 1939 and ending with Japan’s surrender six years later, the war spanned three continents and left as many as 60 million people dead by some estimates. Though the war ended nearly 80 years ago, its impact on geopolitics and international relations remain evident today.
Between the more than 50 countries that were actively engaged in the fighting, over 100 million troops were deployed throughout the conflict, according to the National WWII Museum. In some cases, leading military powers enlisted the equivalent of over 20% of their total population.
Using data compiled by Statista, 24/7 Wall St. identified the biggest armies in World War II. Countries are ranked by the total estimated number of troops mobilized during the war. We only considered the 22 countries with available data that mobilized over 200,000 troops.
Though the United States did not officially join the war until Japan bombed Pearl Harbor, about two years after Germany invaded Poland, the American war effort ramped up quickly. Not only did the U.S. put its industrial might into mass weapons and material production, it also mobilized an estimated 16.4 million troops, more than all countries but Germany and Russia, which mobilized 18.1 million and 34.7 million troops, respectively. (Here is a look at the countries with the 20 strongest militaries.)
In the European Theater, fighting between Germany and Russia on the Eastern Front was especially devastating. The attempted German invasion of Russia, known as Operation Barbarossa, resulted in some of the deadliest battles and sieges in history. Partially as a result, no country suffered more deaths – both civilian and military deaths – than Russia during the war. More than 23 million Russians are estimated to have been killed in WWII. For context, American deaths are estimated to have totaled less than half a million. (Here is a look at the most devastating battles in recent history.)
Click here to see the nations that mobilized the most troops during WWII.
Click here to read our detailed methodology.
Source: Fox Photos / Hulton Archive via Getty Images
22. New Zealand
> Total troops mobilized: Approx. 204,000 (12.4% of pop.)
> War deaths: Approx. 11,671 military (0.7% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 1,641,600
> Date entered war: Sept. 3, 1939
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Source: FPG / Archive Photos via Getty Images
21. South Africa
> Total troops mobilized: Approx. 330,000 (3.2% of pop.)
> War deaths: Approx. 11,900 military (0.1% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 10,160,000
> Date entered war: Sept. 4, 1939
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Source: Public Domain / Wikimedia Commons
20. Netherlands
> Total troops mobilized: Approx. 400,000 (4.6% of pop.)
> War deaths: Approx. 7,900 military; 198,000 civilian (2.4% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 8,729,000
> Date entered war: May 10, 1940
Source: Public Domain / Wikimedia Commons
19. Bulgaria
> Total troops mobilized: Approx. 450,000 (7.0% of pop.)
> War deaths: Approx. 22,000 military; 3,000 civilian (0.4% of pop.)
> Side of conflict: Axis and later the Allies
> National population in 1939: Approx. 6,458,000
> Date entered war: April 20, 1941
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Source: Public Domain / Wikimedia Commons
18. Greece
> Total troops mobilized: Approx. 540,000 (7.5% of pop.)
> War deaths: Approx. 20,000 military; 400,000 civilian (5.8% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 7,222,000
> Date entered war: Oct. 28, 1940
17. Hungary
> Total troops mobilized: Approx. 600,000 (6.6% of pop.)
> War deaths: Approx. 300,000 military; 680,000 civilian (10.7% of pop.)
> Side of conflict: Axis
> National population in 1939: Approx. 9,129,000
> Date entered war: June 27, 1941
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Source: Keystone / Hulton Archive via Getty Images
16. Belgium
> Total troops mobilized: Approx. 600,000 (7.2% of pop.)
> War deaths: Approx. 12,100 military; 76,000 civilian (1.1% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 8,387,000
> Date entered war: May 10, 1940
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Source: Keystone / Hulton Archive via Getty Images
15. Finland
> Total troops mobilized: Approx. 650,000 (17.6% of pop.)
> War deaths: Approx. 95,000 military; 2,000 civilian (2.6% of pop.)
> Side of conflict: Possessed by Axis powers, ultimately declared war on Germany
> National population in 1939: Approx. 3,700,000
> Date entered war: Nov. 30, 1939
Source: Hulton Archive / Hulton Archive via Getty Images
14. Australia
> Total troops mobilized: Approx. 1,000,000 (14.4% of pop.)
> War deaths: Approx. 39,366 military; 735 civilian (0.6% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 6,936,000
> Date entered war: Sept. 3, 1939
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Source: Stanley Sherman / Hulton Archive via Getty Images
13. Canada
> Total troops mobilized: Approx. 1,100,000 (9.8% of pop.)
> War deaths: Approx. 45,300 military (0.4% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 11,267,000
> Date entered war: Sept. 10, 1939
12. Yugoslavia
> Total troops mobilized: Approx. 1,500,000 (9.7% of pop.)
> War deaths: Approx. 446,000 military; 581,000 civilian (6.7% of pop.)
> Side of conflict: Axis, eventually invaded by Germany
> National population in 1939: Approx. 15,400,000
> Date entered war: April 6, 1941
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Source: Archive Photos / Archive Photos via Getty Images
11. Romania
> Total troops mobilized: Approx. 2,000,000 (10.0% of pop.)
> War deaths: Approx. 370,000 military; 533,000 civilian (4.5% of pop.)
> Side of conflict: Axis and later the Allies
> National population in 1939: Approx. 19,934,000
> Date entered war: June 22, 1941
Source: A. J. O'Brien / Hulton Archive via Getty Images
10. Poland
> Total troops mobilized: Approx. 2,000,000 (5.8% of pop.)
> War deaths: Approx. 400,000 military; 5,200,000 civilian (16.1% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 34,775,000
> Date entered war: Sept. 1, 1939
Source: A. R. Tanner / Hulton Archive via Getty Images
9. India
> Total troops mobilized: Approx. 2,581,000 (0.7% of pop.)
> War deaths: Approx. 87,000 military; 1,500,000 civilian (0.4% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 378,000,000
> Date entered war: Sept. 3, 1939
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Source: Evening Standard / Hulton Archive via Getty Images
8. France
> Total troops mobilized: Approx. 5,000,000 (12.0% of pop.)
> War deaths: Approx. 212,000 military; 260,000 civilian (1.1% of pop.)
> Side of conflict: Allies (the puppet state of Vichy France was an Axis power)
> National population in 1939: Approx. 41,700,000
> Date entered war: Sept. 3, 1939
Source: cjp / iStock via Getty Images
7. United Kingdom
> Total troops mobilized: Approx. 5,896,000 (12.3% of pop.)
> War deaths: Approx. 382,600 military; 67,800 civilian (0.9% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 47,760,000
> Date entered war: Sept. 3, 1939
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Source: Hulton Archive / Hulton Archive via Getty Images
6. Japan
> Total troops mobilized: Approx. 9,100,000 (12.7% of pop.)
> War deaths: Approx. 2,000,000 military; 600,000 civilian (3.6% of pop.)
> Side of conflict: Axis
> National population in 1939: Approx. 71,380,000
> Date entered war: July 7, 1937 (beginning of the Second Sino-Japanese War)
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Source: Hulton Archive / Hulton Archive via Getty Images
5. Italy
> Total troops mobilized: Approx. 9,100,000 (20.5% of pop.)
> War deaths: Approx. 306,400 military; 153,100 civilian (1.0% of pop.)
> Side of conflict: Axis
> National population in 1939: Approx. 44,394,000
> Date entered war: June 10, 1940
Source: FPG / Archive Photos via Getty Images
4. China
> Total troops mobilized: Approx. 14,000,000 (2.7% of pop.)
> War deaths: Approx. 4,000,000 military; 16,000,000 civilian (3.9% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 517,568,000
> Date entered war: July 7, 1937 (beginning of the Second Sino-Japanese War)
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Source: Fox Photos / Hulton Archive via Getty Images
3. United States
> Total troops mobilized: Approx. 16,354,000 (12.5% of pop.)
> War deaths: Approx. 407,318 military; 11,200 civilian (0.3% of pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 131,028,000
> Date entered war: Dec. 7, 1941
Source: Hulton Archive / Hulton Archive via Getty Images
2. Germany
> Total troops mobilized: Approx. 18,100,000 (22.7% of pop.)
> War deaths: Approx. 5,500,000 military; 2,000,000 civilian (9.4% of pop.)
> Side of conflict: Axis
> National population in 1939: Approx. 79,800,000
> Date entered war: Sept. 1, 1939
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Source: Yevgeny Khaldei / Hulton Archive via Getty Images
1. Soviet Union
> Total troops mobilized: Approx. 34,746,000 (31.8% of pop.)
> War deaths: Approx. 10,700,000 military; 12,500,000 civilian (21.2% of Russian pop.)
> Side of conflict: Allies
> National population in 1939: Approx. 109,300,000 (Russia)
> Date entered war: Sept. 17, 1939
Methodology
To identify the biggest armies in World War II, 24/7 Wall St. used data compiled by Statista. Countries are ranked by the total estimated number of troops mobilized during the war. We only considered the 22 countries with available data that mobilized over 200,000 troops.
Supplemental data on military and civilians killed and population totals in 1939 are estimates from the World War II Database, an online compilation of historical facts pertaining to the war.
Troop totals are estimates only and, in some cases, represent troops who fought for both the Allied and Axis powers. Though the war began in Europe in 1939, for the purposes of this story, the war is considered to have begun in 1937 for both China and Japan with the outbreak of Second Sino-Japanese War.
Troop mobilization estimates for Italy vary considerably, depending on the source, and may include Libyan and East African troops. Estimates for Japan may also include Thai troops as well as troops from Japanese colonies like Korea and Taiwan. Troop estimates for Romania may overlap with troop counts from Yugoslavia and Croatia.
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