In August 1914 the world exploded into a war that would last four years and kill nearly nine million soldiers. By its end it would change the world forever. The conflict had many causes. It started with the assassination of Austrian Archduke Franz Ferdinand, a move blamed by some leaders on Serbian nationalists. But it also reflected the fact that nations had spent enormous sums on building huge armies and navies in an arms race, creating tensions between countries. It was a war of empires, as major powers sought to expand their territories and influence in the world.

The assassination triggered a chain reaction in which Austria-Hungary declared war on Serbia, then allied with Germany and Russia against France, a move that put the other major powers into a deadly tangle of alliances. The situation became even more complicated as a series of diplomatic crises and diplomatic squabbles erupted, threatening to plunge the world into a global conflict.

In addition, economic pressures brought about a rise in aggressive nationalism, with Germany seeking to reverse the Treaty of Versailles and Japan seeking empire and resources. The result was a world divided into two opposing military alliances: the Allies led by Britain and her empire, the United States and the Soviet Union, against the Axis Powers of Nazi Germany, Fascist Italy and Imperial Japan. As a result, the Allies won the war and the Axis Powers lost. But it was a terrible price. It cost about 65 million lives, both military and civilian, and wiped out entire civilizations.