The First World War broke out on August 4, 1914, when the Archduke Franz Ferdinand of Austria-Hungary was assassinated in Sarajevo, Serbia. He was the heir to the Austro-Hungarian Empire, and a supporter of the Kingdom of Serbia. The Austrian army quickly invaded Serbia, and within months, the war was declared. Within a year, military alliances had been formed throughout Europe, and the countries of Europe and Asia were now fighting each other for dominance.
At the beginning of the war, the United States maintained its neutrality, but it was not enough to keep the nation out of the conflict. German aggression increased after the sinking of the British ocean liner RMS Lusitania, which carried over a hundred Americans. In response, Woodrow Wilson called for a moratorium on unrestricted submarine warfare and other violations of international law. But the war was far from over. Woodrow Wilson’s policy of hyper-vigilance in the United States failed to prevent the war.
After the defeat of Austrian forces in the Piave, the Germans extended their front and battled their Austrian allies in the Caucasus. In the meantime, the French, British, and Americans counter-attacked, forcing the Germans to retreat. In May 1941, the Anglo-French forces at Salonika fought a series of battles along the Isonzo River in northern Italy. The First Battle of the Isonzo, or the First Battle of Ypres, took place shortly after the Italians entered the war. The Twelfth Battle, known as the Battle of Caporetto, ended with an Austrian victory.