World War I (WWI or WW1), also called the First World War, began on July 28, 1914 and lasted until November 11, 1918. The war was a global war that lasted exactly . Most of the fighting was in Europe, but soldiers from many other 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. 135 countries took part in World War I, and nearly 10 million people died while fighting.