World War 2 was a global conflict that lasted from 1939 to 1945 and involved the majority of the world's nations, including all of the great powers, organized into two opposing military alliances: the Allies and the Axis. It was the deadliest conflict in human history, with an estimated 50-85 million fatalities.

The war began with the invasion of Poland by Nazi Germany in September 1939, and quickly spread as Germany conquered much of Europe. In 1941, Germany turned its attention to the Soviet Union and, with the help of its allies, launched a massive invasion. At the same time, Japan attacked the United States at Pearl Harbor, which led to America's entry into the war.

The Allies, consisting of the United States, the United Kingdom, and the Soviet Union, eventually gained the upper hand, thanks in part to their superior industrial production and strategic use of their naval and air power. In 1942, the Allies launched a successful invasion of North Africa, which was followed by the invasion of Italy and the eventual liberation of Europe through the D-Day invasion of Normandy in 1944. Meanwhile, in the Pacific, the Allies engaged in a series of brutal island-hopping campaigns against Japan, ultimately leading to the dropping of atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August 1945.

The war had far-reaching consequences, including the formation of the United Nations and the establishment of the United States and the Soviet Union as superpowers. It also resulted in the rise of communist governments in Eastern Europe, the beginning of the Cold War, and the start of decolonization movements throughout the developing world.

The horrors of the Holocaust, in which millions of Jews and other minority groups were systematically murdered by the Nazi regime, left a lasting impact on the world and serves as a reminder of the dangers of hatred and prejudice. The legacy of World War 2 continues to shape international relations and world events to this day.