What was World War II?
Answer
The global conflict from 1939-1945
Explanation
World War II was the largest and deadliest war in human history, fought from September 1, 1939 to September 2, 1945, between the Allied Powers and the Axis Powers. The Allied Powers were led by the United States, the United Kingdom, the Soviet Union, China, and France, joined by dozens of smaller nations. The Axis Powers were Germany under Adolf Hitler, Italy under Benito Mussolini, and Imperial Japan under Emperor Hirohito and a militarist government led by figures such as Prime Minister Hideki Tojo.
The war began in Europe on September 1, 1939 when Nazi Germany invaded Poland, prompting Britain and France to declare war on Germany two days later. Earlier aggression had set the stage, including the Japanese invasion of Manchuria in 1931, Italy's invasion of Ethiopia in 1935, and Germany's annexation of Austria in March 1938 and Czechoslovakia in March 1939. The Munich Agreement of September 1938, in which Britain and France allowed Hitler to take the Czech Sudetenland, became the textbook example of failed appeasement.
Germany conquered most of Western Europe by the summer of 1940, including the Netherlands, Belgium, and France in just six weeks during May and June 1940. The Battle of Britain followed, with the Royal Air Force defeating the German Luftwaffe in air combat over southern England. Hitler turned east in June 1941, invading the Soviet Union in Operation Barbarossa, which became the largest military campaign in history.
The United States entered the war on December 8, 1941, the day after Japan attacked the American naval base at Pearl Harbor in Hawaii. Germany and Italy declared war on the United States on December 11, 1941. The war was fought across Europe, North Africa, the Atlantic, the Soviet Union, the Pacific, and East Asia.
Total deaths reached 70 to 85 million, including roughly six million Jews murdered in the Holocaust and tens of millions of Soviet civilians and soldiers. About 16 million Americans served, and 405,000 died. Germany surrendered on May 8, 1945, and Japan surrendered on September 2, 1945 after the United States dropped atomic bombs on Hiroshima on August 6 and Nagasaki on August 9. The war reshaped global power, creating two superpowers, the United States and the Soviet Union, and producing the United Nations.
Why this matters for your test
USCIS asks about World War II because it is the defining conflict of the twentieth century and the moment the United States became a global superpower. Understanding the basic dates, sides, and outcome helps applicants connect to questions about the United Nations, the Cold War, and modern American foreign policy.
Source: USCIS 128 Civics Questions (2025)
