The document summarizes the events leading up to and during World War 1. Rising tensions between European powers due to nationalism, militarism, and imperialism led to the formation of opposing alliances. A crisis in the Balkans triggered the war after the assassination of Archduke Franz Ferdinand. The war quickly escalated as countries honored their alliance obligations. Though initially expected to be short, the war resulted in bloody trench warfare and a stalemate on the Western Front. The US entry into the war in 1917 tipped the balance in favor of the Allies. An armistice in 1918 ended the war, but the Treaty of Versailles caused resentment in Germany, paving the way for WWII.