World War II

The deadliest conflict in history, 1939–1945 — and mostly a war against civilians: Britannica's analysis finds civilian deaths probably exceeded battle casualties, with Poland losing a fifth of its people.

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Country

International

Also called

The Second World War

When

1939–1945; began September 1, 1939 (Germany invades Poland), ended with Japan's defeat in August–September 1945

Coalitions

Axis powers (Germany, Italy, Japan) vs Allies (France, Great Britain, the United States, the Soviet Union, China)

Death toll

Estimates range from 35,000,000 to 60,000,000 — statistics are inexact; the Soviet Union and China suffered the most

Character

A 'total war' in which civilians became direct targets of aerial attack; civilian deaths probably exceeded battle casualties

Aftermath

Soviet power extended across Eastern Europe; a communist movement eventually took power in China; global power shifted from Western Europe to the United States and Soviet Union; the five principal Allies became the permanent members of the UN Security Council

Mostly a war against civilians

World War II — the conflict that “involved virtually every part of the world during the years 1939–45” — was in many respects a continuation, after an uneasy 20-year hiatus, of the disputes left unsettled by World War I. The principal belligerents were the Axis powers (Germany, Italy, Japan) and the Allies (France, Great Britain, the United States, the Soviet Union and China) — the five countries that would become the permanent members of the United Nations Security Council.

What set it apart was its total nature: civilian populations “not only contributed to the war effort but also became direct targets of aerial attack,” and in 1941 the Nazi regime unleashed a war of extermination against Jews, Slavs and others deemed inferior, while Stalinist Russia extended its terror to the conquered Poles. Britannica’s cost analysis is blunt: civilian deaths — from land battles, bombardment, executions, war-induced disease and famine, and sinkings — “probably exceeded battle casualties.”

The numbers are famously uncertain. Only the United States and the British Commonwealth have official figures that can be cited with assurance; elsewhere, “statistical accounting broke down” amid surrendered armies, guerrilla warfare, redrawn boundaries and mass population shifts. Estimates of the total dead range from 35 to 60 million. The Soviet Union and China are believed to have suffered most; the heaviest proportionate losses fell on eastern Europe — Poland lost perhaps 20 percent of its prewar population (5.8 million dead, of whom 5,675,000 were civilians), Yugoslavia and the Soviet Union around 10 percent — while about 5.7 million Jews, more than half of them from Poland, died in Nazi concentration and death camps.

How it unfolded

By early 1939 Hitler was determined to invade Poland; secret negotiations produced the German-Soviet Nonaggression Pact of August 23–24, whose secret protocol assigned Poland’s western third to Germany and eastern two-thirds to the USSR. At 12:40 p.m. on August 31, Hitler ordered the attack for 4:45 the next morning; 45 German divisions invaded on September 1, and Britain and France declared war on September 3.

The war widened in 1941: Germany’s invasion of the Soviet Union on June 22, and Japan’s December 7/8 attacks on Pearl Harbor and other American, Dutch and British installations, made it a genuinely world war. Its turning points were Midway (June 3–6, 1942), which destroyed Japan’s first-line carrier force, and Stalingrad (February 1943), where the destruction of two German armies began the end of the Third Reich. The Normandy landings of June 6, 1944 opened the second front; Hitler’s suicide on April 30, 1945 was followed by Europe’s surrender on May 8, and the atomic bombings of Hiroshima and Nagasaki in August knocked Japan out of the war.

What this profile does not claim

A precise death toll; the sources emphasize the figures are estimates of varying reliability, with no reliable numbers for the USSR or China.
Theater-by-theater battle detail; only the turning points Britannica identifies are covered.
Post-war settlements, war-crimes trials, or the Holocaust’s full scope beyond the figures Britannica publishes here.

Timeline

Sources

2 sources (2 tier 2), each opened and read against the claim it supports. Every source is independent of the subject; no first-party material is cited. See the source policy.