High School World History · 1939–1945
How a broken peace, a world depression, and aggressive dictatorships led to the deadliest war in history.
Twenty-one years after the guns fell silent in 1918, German tanks rolled into Poland. Six years later, much of Europe and Asia lay in ruins, tens of millions of people were dead, and two atomic bombs had shown the world a terrible new power.
I am Herodotus, and I wrote so that the deeds of people would not be forgotten. This war asks harder questions than any I faced. How did the peace of 1919 fail? How did a modern nation carry out the murder of six million Jews? And what did the survivors build so that it would never happen again?
World War II was fought from 1939 to 1945 between the Allies (led by Britain, the Soviet Union, the United States, and China) and the Axis (Germany, Italy, and Japan, with partners such as Hungary, Romania, and Bulgaria). Japan had been at war with China since 1937.
It was the deadliest war in history. Estimates of the dead range from about 40–50 million (Encyclopaedia Britannica) to 60 million or more (the National WWII Museum), most of them civilians. Germany surrendered on May 8, 1945 (V-E Day). Japan announced its surrender on August 15, 1945 and signed it on September 2, 1945.
No single event caused World War II. Historians point to several long-term pressures that weakened the peace of 1919, and to a chain of crises in the 1930s when aggressive governments tested the democracies and found them unwilling to fight.
Many Germans hated the 1919 Treaty of Versailles. They resented the "war guilt" clause, the reparations bill, the lost land, and the tiny army it allowed. Nationalist politicians promised to tear the treaty up. Italy and Japan, though on the winning side in 1918, also felt cheated by the peace.
The Wall Street crash of October 1929 set off a worldwide depression. Banks failed, trade collapsed, and millions lost their jobs. In Germany, mass unemployment made voters desperate, and they turned to extreme parties that promised quick answers.
Benito Mussolini made Italy the first fascist state after 1922. Adolf Hitler became chancellor of Germany on January 30, 1933, and turned it into a one-party dictatorship within months. Nazism glorified the nation and war, crushed opponents, and was built on racism and hatred of Jews. Hitler wanted "living space" (Lebensraum) for Germans in Eastern Europe.
Military leaders in Japan wanted an empire in Asia to supply raw materials. In September 1931, the Japanese army seized Manchuria in northeast China. When the League of Nations condemned it, Japan simply left the League. In July 1937, Japan launched a full-scale war on China.
Britain and France, still scarred by World War I, wanted to avoid another war almost at any cost. Their policy of appeasement meant giving in to some demands in the hope that the dictators would be satisfied. The League of Nations, without the United States, proved too weak to stop aggression.
The dates show when each country went to war. Some countries changed sides or were knocked out of the war along the way.
Germany, Italy, and Japan signed the Tripartite Pact on September 27, 1940, promising to help each other if a new power, meaning the United States, entered the war against them.
On September 1, 1939, Germany invaded Poland. Britain and France declared war on Germany two days later, on September 3. On September 17, the Soviet Union invaded Poland from the east, as the secret protocol had planned. Poland was crushed within weeks and divided between its two neighbors.
Germany's way of fighting became known as Blitzkrieg ("lightning war"): tanks, motorized troops, and dive-bombers punched through enemy lines and raced ahead before the defenders could recover. It was a shock after the slow trench warfare of 1914–1918.
After quiet months known as the "Phoney War," and the conquest of Denmark and Norway in April, Germany struck west on May 10, 1940. Its tanks crossed the Ardennes forest and cut the Allied armies in two. From May 26 to June 4, about 338,000 British and French troops were rescued from the beaches of Dunkirk. Italy declared war on June 10. Paris fell on June 14, and France signed an armistice on June 22. Germany occupied the north and west, and a collaborating French government ruled the rest from the town of Vichy.
Before Germany could invade Britain, it needed control of the skies. Britain's new prime minister, Winston Churchill, refused to make peace. RAF fighter pilots, helped by radar, fought off the Luftwaffe, and Hitler postponed the invasion. Germany then bombed British cities by night in the Blitz, from September 1940 to May 1941.
Breaking the Nazi-Soviet Pact, Germany and its allies invaded the Soviet Union with more than three million troops along a front from the Baltic to the Black Sea. They surrounded whole Soviet armies and besieged Leningrad, where hundreds of thousands of civilians starved. In December 1941, in bitter cold, a Soviet counterattack threw the Germans back from the edge of Moscow. Hitler's hope of a quick victory was gone.
The United States stayed officially neutral, but it moved closer to Britain. The Lend-Lease Act of March 11, 1941, let President Franklin D. Roosevelt send weapons and supplies to Britain, and later to the Soviet Union and China. In August 1941, Roosevelt and Churchill issued the Atlantic Charter, a statement of shared war aims.
For China, the war began in July 1937, when fighting near Beijing grew into a full Japanese invasion. Japanese forces took the coast and the major cities. When they captured the Chinese capital, Nanjing, in December 1937, they murdered tens of thousands of civilians and prisoners and raped many women; Chinese and Japanese historians still dispute how many died. China's government, led by Chiang Kai-shek, retreated inland to Chongqing and kept fighting, as did Communist forces led by Mao Zedong.
Japan wanted the oil, rubber, and tin of Southeast Asia. In 1941, the United States answered Japan's advance into French Indochina by cutting off oil exports. Japan's leaders decided to seize what they needed and to knock out the US Pacific Fleet first.
Japanese carrier planes made a surprise attack on the US naval base at Pearl Harbor. They sank or damaged nearly 20 American ships, including eight battleships, destroyed or damaged more than 300 aircraft, and killed 2,403 Americans, 68 of them civilians. The US aircraft carriers were at sea and escaped. The next day, Congress declared war on Japan. On December 11, Germany and Italy declared war on the United States.
In a few months, Japan took Hong Kong, Malaya, the Philippines, the Dutch East Indies, Burma, and many Pacific islands. The British base at Singapore surrendered on February 15, 1942. In the Philippines, Japanese troops forced American and Filipino prisoners on the brutal Bataan Death March in April 1942.
US code breakers learned of Japan's plan to attack Midway. American carrier planes ambushed the Japanese fleet and sank four of its aircraft carriers, losing one carrier of their own. Japan never recovered its naval strength. Midway was the turning point of the Pacific war.
From August 1942 to February 1943, US forces fought a long, bloody campaign for Guadalcanal in the Solomon Islands. After that, the Allies used island hopping (also called leapfrogging): instead of attacking every Japanese-held island, they captured key islands for airfields and bases and bypassed others, cutting them off. One drive crossed the central Pacific through Tarawa, the Marshall Islands, and Saipan. Another, under General Douglas MacArthur, moved along New Guinea to the Philippines. The Battle of Leyte Gulf in October 1944, one of the largest naval battles in history, destroyed most of what was left of Japan's navy. Japan began sending kamikaze pilots on suicide attacks against Allied ships.
In 1942 the Axis controlled more territory than at any other time. Within about a year, the Allies had stopped them on every front. The Soviet Union did much of the fighting against Germany: most German soldiers who died in the war died on the Eastern Front.
German forces pushed toward the oil fields of the Caucasus and fought their way into Stalingrad, street by street. On November 19, 1942, the Red Army launched a counterattack that trapped the German Sixth Army inside the city. Starving and frozen, the Germans surrendered between January 31 and February 2, 1943. After Stalingrad, Germany was mostly in retreat in the east. In July 1943, it lost the huge tank battle at Kursk, its last major offensive there.
The British Eighth Army beat General Erwin Rommel's Axis army at El Alamein in Egypt (October 23 – November 11, 1942). On November 8, 1942, American and British troops landed in Morocco and Algeria (Operation Torch). The last Axis forces in Africa surrendered in Tunisia in May 1943. The Allies invaded Sicily on July 10, 1943. Mussolini was overthrown on July 25, and Italy surrendered in September, but German troops occupied Italy and fought on. Rome was freed on June 4, 1944.
German U-boats hunted the convoys of merchant ships carrying food, fuel, and weapons to Britain. By the spring of 1943, escort ships, long-range aircraft, radar, and code breaking at Bletchley Park, where British experts read the German Enigma code, had turned the battle in the Allies' favor.
The Soviet leader Joseph Stalin had long demanded a "second front" in Western Europe. It came on June 6, 1944, when Allied forces under General Dwight D. Eisenhower landed in Normandy, France, in Operation Overlord. About 156,000 American, British, Canadian, and other Allied troops came ashore by sea and air on that first day, on five beaches code-named Utah, Omaha, Gold, Juno, and Sword. More than 5,000 ships and 11,000 aircraft supported them. The Allies suffered more than 10,000 casualties that day, including 4,414 confirmed dead.
After weeks of hard fighting in the hedgerows of Normandy, the Allies broke out. Paris was liberated on August 25, 1944. In the east, a massive Soviet offensive that began in June 1944 destroyed a whole German army group and drove the Germans out of Belarus. Germany's last big attack in the west, the Battle of the Bulge in the Ardennes (December 16, 1944 – January 25, 1945), failed.
Like World War I, this was a total war. Factories, farms, and families were all part of the war effort, and civilians were often in the line of fire.
About 16.4 million Americans served in the armed forces, including about 350,000 women. At home, women took factory and shipyard jobs, celebrated by the figure of "Rosie the Riveter." Families used ration books for goods such as sugar, meat, and gasoline, and bought war bonds to pay for the war. Black Americans, who served in segregated units, campaigned for a "Double Victory": over fascism abroad and racism at home.
On February 19, 1942, President Roosevelt signed Executive Order 9066. The government forced about 120,000 people of Japanese ancestry on the West Coast, about two-thirds of them US citizens, from their homes into remote camps. No evidence showed they were disloyal. In 1988, Congress formally apologized and paid compensation to survivors.
Food rationing began on January 8, 1940, with bacon, butter, and sugar, and later spread to meat, tea, cheese, and clothing. Children were evacuated from cities to the countryside to escape bombing. During the Blitz, families slept in shelters and London Underground stations. From December 1941, Britain conscripted unmarried young women for war work and the auxiliary services.
The Soviets moved whole factories east of the Ural Mountains, beyond the reach of German armies, and women worked in industry and served as soldiers, snipers, and pilots. Nazi Germany forced millions of people from occupied countries to work as slave and forced laborers. In Japan, food ran short, and US firebombing raids burned large parts of its cities; the raid on Tokyo on March 9–10, 1945, killed about 100,000 people (estimates vary) in one night.
The United States Holocaust Memorial Museum (USHMM) defines the Holocaust as "the systematic, state-sponsored persecution and murder of six million European Jews by the Nazi German regime and its allies and collaborators" between 1933 and 1945. Antisemitism, hatred of or prejudice against Jews, was a basic belief of Nazism. The Nazis also persecuted and murdered millions of other people they considered enemies or "inferior."
This section deals with mass murder. It is meant to be read carefully, not quickly. Behind every number is a person with a name, a family, and a community.
| Where and how | Number of Jews murdered |
|---|---|
| Killing centers (poison gas) | About 2.7 million |
| Mass shootings and related massacres, in more than 1,500 cities, towns, and villages | About 2 million |
| Ghettos, labor camps, and concentration camps (starvation, disease, brutal treatment) | 800,000 to 1 million |
| Other violence outside camps and ghettos, including death marches | At least 250,000 |
The Nazis and their allies and collaborators also murdered about 3.3 million Soviet prisoners of war, about 1.8 million non-Jewish Poles, between 250,000 and 500,000 Roma, 250,000 to 300,000 people with disabilities, and more than 310,000 Serb civilians killed by the Ustaša regime in Croatia, as well as political opponents, Jehovah's Witnesses, gay men, and others (USHMM).
Jews resisted in many ways: by smuggling food, keeping schools and diaries, hiding, escaping, and fighting. On April 19, 1943, Jewish fighters in the Warsaw ghetto rose up against the Germans and held out for about a month. There were also revolts at Treblinka and Sobibor in 1943. Some non-Jews risked their lives to hide Jews. In October 1943, Danish citizens helped more than 7,000 Jews escape by boat to neutral Sweden.
As Allied armies advanced, they reached the camps. Soviet troops liberated Auschwitz on January 27, 1945. American troops reached Ohrdruf in April 1945 and Buchenwald soon after, and British troops entered Bergen-Belsen, where the teenage diarist Anne Frank had died weeks earlier. The soldiers found starving survivors and thousands of unburied dead. General Eisenhower insisted that reporters, politicians, and his own troops see the camps, so that no one could later deny what had happened (see his letter in Primary Sources).
In February 1945, Churchill, Roosevelt, and Stalin met at Yalta in Crimea. They agreed to divide a defeated Germany into zones of occupation, to create a new world organization, and that the Soviet Union would join the war against Japan after Germany's defeat. Roosevelt died on April 12, 1945, and Vice President Harry S. Truman became president.
Soviet armies fought their way into Berlin in April. Italian partisans killed Mussolini on April 28, and Hitler killed himself in his Berlin bunker on April 30. Germany signed an unconditional surrender at Reims, France, on May 7, to take effect the next day. May 8, 1945, became V-E Day (Victory in Europe Day). A second signing in Berlin took effect after midnight Moscow time, so Russia marks the victory on May 9.
The war in the Pacific grew even bloodier as Allied forces neared Japan. The battles of Iwo Jima (February 19 – March 26, 1945) and Okinawa (April 1 – June 22, 1945) caused tens of thousands of American casualties, and on Okinawa many thousands of local civilians died as well. American leaders expected an invasion of Japan's home islands to be far worse. On July 26, the Allies' Potsdam Declaration warned Japan to surrender unconditionally or face "prompt and utter destruction."
The United States had secretly built the atomic bomb in the Manhattan Project and tested it in New Mexico on July 16, 1945. On August 6, 1945, a US bomber dropped an atomic bomb on Hiroshima. On August 8, the Soviet Union declared war on Japan and invaded Manchuria. On August 9, a second bomb destroyed much of Nagasaki. By the end of 1945, about 140,000 people had died in Hiroshima and about 74,000 in Nagasaki, from the blasts, the fires, and radiation sickness.
On August 15, 1945 (August 14 in the United States), Emperor Hirohito announced on the radio that Japan would surrender. The formal surrender was signed aboard the battleship USS Missouri in Tokyo Bay on September 2, 1945, which the United States marks as V-J Day (Victory over Japan Day). World War II was over.
No one knows exactly how many people died in World War II. Records were lost or never kept, borders changed, and historians count differently, for example in whether they include deaths from famine and disease. Estimates of the total range from about 40–50 million (Encyclopaedia Britannica) to 60 million or more. The National WWII Museum estimates about 15 million battle deaths and about 45 million civilian deaths, and warns that estimates vary widely. Unlike in World War I, far more civilians died than soldiers.
Figures are the National WWII Museum's estimates of total military and civilian deaths, rounded; where it gives a range, the bar shows the middle of the range. Other sources give different numbers, especially for the Soviet Union and China. Polish and Soviet totals include millions of Jews murdered in the Holocaust.
Fifty nations signed the UN Charter in San Francisco on June 26, 1945, and the United Nations came into being on October 24, 1945. Unlike the League of Nations, it included the United States and the Soviet Union from the start. Its Security Council gave five permanent members (the US, the USSR, Britain, France, and China) the power to veto decisions. In 1948, the UN adopted the Genocide Convention and the Universal Declaration of Human Rights.
An International Military Tribunal of judges from the US, Britain, France, and the Soviet Union tried 22 leading Nazis for crimes against peace, war crimes, and crimes against humanity. Nineteen were convicted and 12 were sentenced to death. The trials set the principle that "following orders" does not excuse taking part in atrocities. Japanese leaders were tried in Tokyo from 1946 to 1948.
The wartime alliance soon broke apart. The Soviet Union set up communist governments across Eastern Europe, and Germany, divided into occupation zones, became two countries in 1949. In March 1946, Churchill warned that "an iron curtain has descended across the Continent." The United States and the Soviet Union became rival superpowers in a long Cold War and a nuclear arms race.
The war weakened Britain, France, and the Netherlands and inspired independence movements in their colonies. India and Pakistan became independent in 1947. Over the next three decades, dozens of new nations formed in Asia and Africa.
Follow the war from the crises of the 1930s to the trials and treaties that came after it. Use the buttons to show one kind of event or one year at a time.
The Japanese army uses a staged explosion on a railway as an excuse to occupy northeast China.
Within months, the Nazis ban other parties and turn Germany into a dictatorship.
German Jews lose their citizenship, and marriages between Jews and other Germans are banned.
The League of Nations imposes weak sanctions that fail to stop Mussolini.
German troops enter the zone that the Treaty of Versailles had kept free of soldiers.
A clash near Beijing grows into a full-scale Japanese invasion of China.
Japanese troops capture China's capital and murder tens of thousands of civilians and prisoners.
German troops march into Austria, which is annexed to Germany.
Britain and France agree to let Germany take the Sudetenland from Czechoslovakia.
Nazi-led mobs burn synagogues and attack Jewish homes and shops across Germany and Austria.
Hitler breaks the Munich deal. Britain and France promise to defend Poland.
Germany and the Soviet Union agree not to fight each other and secretly divide Eastern Europe.
The Soviet Union invades Poland from the east on September 17.
They declare war on Germany but can do little to save Poland.
Bacon, butter, and sugar are the first foods rationed.
Germany invades the Netherlands, Belgium, Luxembourg, and France. Churchill becomes prime minister the same day.
About 338,000 Allied troops are rescued from the French coast.
Germany occupies northern and western France; a collaborating regime rules from Vichy.
The RAF defends Britain against the Luftwaffe until the end of October.
German bombers start months of raids on London and other British cities.
The still-neutral United States starts sending war supplies to Britain and, later, other Allies.
Germany and its allies invade the Soviet Union.
German units shoot 33,771 Jews in a ravine outside Kyiv.
Japan strikes the US fleet in Hawaii. The US declares war on Japan the next day.
The United States is now at war in both Europe and the Pacific.
Nazi officials coordinate the "Final Solution," the murder of Europe's Jews.
Britain's main base in Asia falls to Japan.
About 120,000 people of Japanese ancestry are forced into camps in the US.
The US Navy sinks four Japanese aircraft carriers.
US Marines land in the Solomon Islands; the fight lasts until February 1943.
The British Eighth Army defeats Rommel in Egypt.
American and British troops land in Morocco and Algeria.
The Red Army traps the German Sixth Army in the city.
The last German troops in the city give up.
Jewish fighters resist German troops for about a month.
Mussolini is overthrown two weeks later.
US Marines take the atoll in three days of heavy fighting.
About 156,000 Allied troops land in Normandy, France.
Its capture puts Japan within range of US bombers.
Free French and American troops enter the city.
The US Navy destroys most of Japan's remaining fleet off the Philippines.
Germany's last major attack in the west fails by late January.
Soviet troops find about 7,000 prisoners still alive in the camp.
Roosevelt, Churchill, and Stalin plan the defeat and occupation of Germany.
US Marines land; the fighting lasts until March 26.
A US air raid burns much of the city and kills about 100,000 people (estimates vary).
The last great battle of the Pacific war lasts until June 22.
Harry S. Truman becomes president of the United States.
Germany's unconditional surrender takes effect. The war in Europe is over.
Fifty nations sign the charter in San Francisco.
About 140,000 people are dead by the end of 1945.
About 74,000 people are dead by the end of 1945. The day before, the Soviet Union declared war on Japan.
Emperor Hirohito speaks to his people by radio (August 14 in the US).
Japan signs the surrender aboard USS Missouri in Tokyo Bay.
The UN Charter comes into force.
Twenty-two Nazi leaders go on trial before an international tribunal.
In Fulton, Missouri, Churchill warns of Soviet control of Eastern Europe.
Nineteen defendants are convicted and 12 are sentenced to death.
The UN General Assembly adopts it in Paris.
A primary source was made by people who lived through the events. Read each one closely and ask: Who made this? When? Why? Who was the audience?
"Yesterday, December 7, 1941—a date which will live in infamy—the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan."
Why it matters: Roosevelt spoke the day after Pearl Harbor. Congress declared war on Japan the same day; only one member of Congress voted no. His reading copy shows he changed "a date which will live in world history" to "infamy."
Think: Why do you think Roosevelt chose the words "suddenly and deliberately"? What did he want Americans to feel?
"…we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender…"
Why it matters: Churchill gave this speech as the evacuation from Dunkirk ended. He warned that "wars are not won by evacuations," but promised that Britain would fight on alone if it had to. France surrendered less than three weeks later.
Think: The speech was given in Parliament, and parts were read out on the radio that evening. How might a speech meant to keep up morale differ from an honest report of the military situation? Does this one do both?
"Soldiers, Sailors and Airmen of the Allied Expeditionary Force! You are about to embark upon the Great Crusade, toward which we have striven these many months. The eyes of the world are upon you. The hopes and prayers of liberty-loving people everywhere march with you."
Why it matters: Copies were handed to the roughly 175,000 men about to cross the English Channel. Eisenhower also wrote a private note taking the blame in case the landings failed; he never had to use it.
Think: Why would Eisenhower call the invasion a "Great Crusade"? Who is included in "liberty-loving people everywhere"?
"The things I saw beggar description. … I made the visit deliberately, in order to be in position to give first-hand evidence of these things if ever, in the future, there develops a tendency to charge these allegations merely to 'propaganda.'"
Why it matters: Ohrdruf, a subcamp of Buchenwald, was the first Nazi camp liberated by US troops. Eisenhower soon asked Marshall to send members of Congress and journalists to see the liberated camps, so that the American public would learn the truth.
Think: Eisenhower expected that some people would one day call the camps "propaganda." Why are eyewitness records like this letter so important for historians today?
Ten questions. Choose an answer for each, then press Check my answers to see your score and an explanation for every question.
Credits: All illustrations, diagrams, and maps on this page are original artwork made for Jugami. Map coastlines and borders are based on public-domain Natural Earth data; wartime borders, occupied areas, and front lines are approximate. Death tolls for this war vary widely by source; we give ranges and name the institutions whose estimates we use. The Churchill excerpt is quoted briefly for teaching from the parliamentary record.