World War II (1939–1945) was a global military conflict fought primarily in Europe, North Africa, the Pacific Ocean, and East Asia. The war pitted the Allied powers of Great Britain, the Soviet Union, the United States, and others against the Axis powers of Germany, Italy, Japan, and their supporters. The war began in September 1939 with Nazi Germany’s invasion of Poland. The Nazi Party was composed of the political and military forces of Adolf Hitler (1889–1945), dictator of Germany. Over the next few years, Germany invaded and took control of almost all of Europe and killed millions of civilians. Meanwhile, the Empire of Japan began aggressively expanding in East Asia by attacking China and various other foreign territories in the Pacific Ocean. The Allies eventually launched counterattacks against Germany in Europe and Japan in the Pacific. The Allies defeated both Germany and Japan in 1945, ending the war. About sixty million people died in World War II.
World War II in Europe grew out of Germany’s defeat in World War I (1914–1918). The country was embarrassed by the terms imposed on it after the war. These terms included, for example, the requirement to pay reparations to countries that Germany attacked in the conflict. The German people’s resentment over the next decade and a half allowed Hitler and his National Socialist German Workers’ Party, or Nazi Party, to come to power in Germany in 1933.
Hitler promised the German people that he would glorify Germany by expanding the country throughout the world through war. At the same time, Hitler planned to eliminate Jewish people and other groups because he believed that they were inferior to the “pure” race of Germans. Hitler spent most of the 1930s building up Nazi Germany’s military power. He agreed to peace treaties with Italy and Japan in the late 1930s, as these countries planned to expand aggressively in their regions of the world. These three nations were the primary members of the Axis powers in World War II. Germany also agreed to a peace treaty with the Soviet Union, but this alliance only lasted a few years.
The War Begins
Germany invaded Poland on September 1, 1939, officially beginning World War II. The United Kingdom and France then declared war on Germany because they promised to defend Poland from a German attack. Meanwhile, the Soviet Union invaded Poland from the east and then took over a number of other Eastern European countries. Germany and the Soviet Union had full control of their own parts of Poland by early 1940.
Hitler continued his conquest of Europe in the spring of 1940. In April and May, Nazi armies invaded Norway, Denmark, Belgium, and the Netherlands, using quick, powerful assaults known as blitzkrieg, or lightning war. Germany then invaded France and quickly gained control of the country in June. About the same time, Benito Mussolini (1883–1945), dictator of Italy, confirmed his solidarity with Hitler by also declaring war on the United Kingdom and France.
Hitler intended to invade the United Kingdom next, but its separation from mainland Europe by the English Channel would have made such an attack difficult. The German air force started bombing the United Kingdom in mid-1940, but the Royal Air Force eventually repelled these attacks in the Battle of Britain. As a result, Germany never invaded the British Isles.
The Second Wave
Hitler starting turning his attention to Europe’s Balkan region in 1941. Bulgaria, Hungary, and Romania joined the Axis powers that year, and Germany soon took control of Yugoslavia and Greece. Hitler also began planning to betray his peace treaty with Soviet leader Joseph Stalin (1878–1953) and invade the Soviet Union. Hitler hoped to use this large country as more living space for the German people.
Germany invaded the Soviet Union in mid-1941 in the Operation Barbarossa campaign. It was initially a success. The Germans made great advances in the invasion and almost reached the Soviet capital of Moscow by July. Later delays in the attack allowed the Soviets enough time to repel the Germans, and Germany’s advance was halted by December 1941.
The German army murdered many Soviet civilians, especially Soviet Jews, during the invasion. This was part of Hitler’s developing plan to exterminate Europe’s Jewish populations. He also targeted other groups such the Roma, gay people, individuals who did not share his political views, and people with physical and mental disabilities. The initiative, which was called the “Final Solution,” later became known as the Holocaust. Hitler’s order called for Jews and other groups throughout Europe to be imprisoned in concentration camps and then murdered in gas chambers. Of the estimated eleven million people killed during the Holocaust, about six million were Jews.
The War Expands
While Germany was spreading its reach throughout Europe, Japan was expanding in East Asia. It already invaded China and Indochina and sought to acquire other European territories in the Pacific Ocean. Seeing the United States as a military threat, Japan bombed the United States’ naval base at Pearl Harbor in Hawaii on December 7, 1941. More than 2,300 American soldiers died in the attack. The next day, the United States declared war on Japan. Days later, Germany and Italy declared war on the United States.
By 1942, the United States joined the United Kingdom, Soviet Union, and various other countries to form the Allied powers. The United States and Japan fought numerous naval battles in the Pacific Ocean in 1942 and 1943. Japan had the advantage in these engagements at first, but the American victory in the 1942 Battle of Midway started turning the course of the war’s Pacific theater in the favor of the United States. US forces started pushing into Japanese-held islands in mid-1943. In the strategy known as island hopping, the United States moved quickly from island to island to clear a path for the eventual invasion of Japan.
Meanwhile, the Germans began suffering major battlefield losses by 1943. British and American troops pushed Germany and Italy out of North Africa that year. This was followed by the Allied invasion of Italy and the toppling of Mussolini’s dictatorship. Germany also lost the especially destructive Battle of Stalingrad in southern Russia in late January 1943. This decisive Soviet victory mostly ended Germany’s eastern offensive. The Soviet Union then began pushing west toward Germany.
Germany still controlled Western Europe in early 1944. The Allies planned for years to open a new theater of combat in this region, but the difficulty of mounting an attack on long-held Nazi territory was considerable. Eventually, the United States and United Kingdom devised an invasion termed Operation Overlord.
The plan called for 156,000 American, British, and Canadian troops under the command of American general Dwight Eisenhower (1890–1969) to launch an amphibious assault, or one involving both sea and land, on the beaches of Normandy in northwest France. The invasion began on June 6, 1944. Allied transports brought the troops across the English Channel and onto the Normandy beaches. Some divisions encountered little German resistance. Other areas of Normandy, such as Omaha Beach, were heavily defended. About 4,000 Allied soldiers died during the invasion, on what became known as D-Day.
Operation Overlord was considered a great success. It allowed the Allies to make their first push into Nazi-occupied Europe. From northwest France, the Allies gradually advanced toward Germany, intending to close in on the country from the west as the Soviets arrived from the east. Having given up the eastern front after his defeat at Stalingrad, Hitler directed his remaining forces to defend Western Europe from the approaching Allies. The last major German offensive of the war was the Battle of the Bulge, which lasted from December 1944 to January 1945. The Allied victory in the battle essentially ensured Germany’s defeat.
Allied planes then started bombing Germany, while Soviet forces retook Eastern Europe. The Allies arrived in Germany by the spring of 1945. The German army was defeated, and Hitler, realizing his failure, killed himself in Berlin on April 30. Germany surrendered to the Allies in early May.
Japan, however, remained at war with the Allies. In mid-1945, US president Harry Truman (1884–1972) decided to use the United States’ newly created atomic bomb on Japan to swiftly end World War II. He chose this option because a land invasion of the Japanese mainland would likely have been extremely dangerous for the Allies. The United States dropped two atomic bombs on Japan in August 1945, one on Hiroshima and one on Nagasaki. More than one hundred thousand people died in the bombings. Japan formally surrendered to the Allies on September 2, 1945. World War II lasted six years and claimed the lives of about sixty million people.