In 1933, Adolf Hitler, leader of the Nazi Party, was appointed chancellor of Germany. He immediately began to prepare for war, rearming the country, engaging in aggressive foreign policy, and establishing dictatorial powers for himself. German rearmament and aggression were in violation of the Treaty of Versailles, which Germany had signed at the end of World War I, and which the Nazi Party repudiated. Even after Hitler annexed Austria and invaded Czechoslovakia in 1938, attempts were made by other European powers to placate him. When Hitler invaded Poland in 1939, however, Great Britain and France declared war on Germany. The war of the Axis powers (Germany, Italy, Japan, Hungary, Romania, and Bulgaria) against the Allied powers (Great Britain and its allies, France, China, Denmark, Greece, Norway, and Yugoslavia) had begun.
The Soviet Union, initially at uneasy peace with Germany, went to war against Germany when Germany invaded the Soviet Union in 1941. Japan, having gone to war against China in 1936, joined the Axis in 1940 and attacked the United States in 1941. The United States thereupon entered the war in 1941 on the Allied side, declaring war on Japan, Germany, and Italy.
World War II was truly a world war, with nations around the world involved in theaters of war around the world. World War II was also a total war; all targets, military and civilian, were considered legitimate, and all means of war, including the bombing of cities, were employed. Total warfare meant that entire societies were affected. The war was global; few people on the planet were completely unaffected. Some of history’s most terrible atrocities took place during World War II, including the Holocaust (the systematic murder of approximately ten million civilians that the Nazis considered unworthy of life) which claimed the lives of approximately six million Jews.
World War II ended with the defeat of Italy in April, 1945, of Germany in May, and of Japan in August. The United States hastened the surrender of Japan with the first use in history of atomic weapons; this act also may be said to be a symbol of the rise of United States to the level of the world’s preeminent power as a result of World War II. The Allies, victorious, made arrangements of territory and political alliance that deeply affected the world thereafter.