The First World War began on July 28, 1914, and lasted until November 11, 1918. It was a global war and lasted exactly 4 years, 3 months, and 2 weeks. Most of the fighting was in continental Europe. Soldiers from many countries took part, and it changed the colonial empires of the European powers. Before World War II began in 1939, World War I was called the Great War, or the World War. Other names are the Imperialist War and the Four Years' War. There were 135 countries that took part in the First World War, and nearly 10 million people died while fighting. Before the war, European countries had formed alliances to protect themselves. However, that made them divide themselves into two groups. When Archduke Franz Ferdinand of Austria was assassinated on June 28, 1914, Austria-Hungary blamed Serbia and declared war on it. Russia then declared war on Austria-Hungary, which set off a chain of events in which members from both groups of countries declared war on each other.
The Second World War was a global war that involved fighting in most of the world. Most countries fought from 1939 to 1945, but some started fighting in 1937. Most of the world's countries, including all of the great powers, fought as part of two military alliances: the Allies and the Axis Powers. It involved more countries, cost more money, involved more people, and killed more people than any other war in history. Between 50 to 85 million people died, most of whom were civilians. The war included massacres, a genocide called the Holocaust, strategic bombing, starvation, disease, and the only use of nuclear weapons against civilians in history.
