World War I was a global war originating in Europe from July 1914 until November 1918. It is also known as The Great War and was one of the deadliest conflicts in history, mobilizing 70 million military personnel and more than 21 million deaths. The cause of the war traces back to the assassination of Austro-Hungarian heir, Archduke Franz Ferdinand, by a Bosnian Serb Yugoslav nationalist. Following this event, instability on the European continent escalated until a month later on July 28, 1914, Austrian-Hungarian forces shelled the Serbian capital of Belgrade, initiating the official start of the war. In the end, the First World War split the continent of Europe into two major opposing groups, the Allied Powers, including the United States, the UK, France, Russia, Italy, Japan, Portugal, Greece, Serbia, and Montenegro. And the Central Powers, which included Germany, the Austro-Hungarian Empire, the Ottoman Empire that is now known as Turkey, and Bulgaria. This was the first war to really divide up the globe in such a monumental way, and the death toll was staggering with the advent of new technologies never previously used in war before—like the very first tank (known as Little Willie), the telephone, and the use of aircraft.