On June 28, 1914, Gavrilo Princip assassinated the Archduke Franz Ferdinand, heir to the throne of Austria-Hungary, and his wife as they made a state visit to Sarajevo, Bosnia. Princip acted on behalf of the Serbian-based Black Hand terrorist group which sought independence for Bosnia, a recently annexed imperial province of the Austro-Hungarian Empire. His desire to see Bosnia united with Serbia eventually came true when the nation of Yugoslavia was founded in 1918. By then, Princip had died in prison, one of countless lives lost during the brutal four-year world war that the assassination triggered. In the wake of Ferdinand’s death, five weeks of indecision ensued. A flurry of increasingly bellicose telegram exchanges among European leaders, heated internal governmental debates, and militaries put on high alert quickly turned a regional dispute into a crisis that threatened the entire European continent. By early August, Austria-Hungary, Russia, and Germany had decided that this was the moment to resolve long-simmering territorial disputes with a quick, decisive war. Their decision for war had grave implications for Serbia, Belgium, France, and Great Britain (and their empires), all quickly pulled into the fray. World War I had begun. Across the Atlantic, President Woodrow Wilson immediately declared the United States neutral in the conflict and urged Americans to remain “impartial in thought as well as action.” Over the next few months, hopes for a short war evaporated amid staggering casualties. On the Eastern Front, Russian and German armies traded huge swaths of land at great cost without producing the expected victory. Along the Western Front, the massive trench defensive system taking shape created a stalemate. In early 1915, as armies regrouped, Great Britain and Germany turned their attention to the seas, hoping to use naval power to bring their enemies to the negotiating table. Britain relied on its naval superiority to create blockades that prevented goods from reaching the Central Powers (Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire). Germany turned to a new weapon, the U-boat, or submarine, to sink cargo, troop, and eventually passenger ships traveling into the war zone. The popular song “I Didn’t Raise My Boy to Be a Soldier” reflected Americans’ general desire to remain on the sidelines of the expanding war. Nonetheless, the conflict increasingly touched the nation. U.S. banks financed a booming trade with the Allies (the British Empire, France, Belgium, Russia, and Italy), which included arms and munitions. Britain had been the nation’s largest prewar trading partner, and now purchased nearly 65 percent of U.S. exports. By contrast, trade with Germany declined considerably, reflecting Americans’ pro-Allied sympathies and an effective British blockade that limited access to German ports. In response, Germany tried to disrupt shipments from the United States with a policy of unrestricted submarine warfare. This decision backfired with the torpedoing and sinking of a British passenger ship, the RMS Lusitania, on May 7, 1915 (See Enlist). The attack killed 1,198 passengers, including women and children, and coincided with the release of an official British report detailing atrocities committed by German troops when they invaded Belgium in 1914. These incidents catalyzed anti-German feelings within the United States. Wilson shied away from entering the war in 1915 and 1916. His rhetoric, however, increasingly lambasted Germany for killing noncombatants and illegally interfering with the rights of neutral nations to use the seas unmolested. In the wake of another controversial sinking that resulted in civilian deaths, he warned Germany that a continuation of unrestricted submarine warfare would result in a break of diplomatic relations with the United States. Relations briefly improved when Germany pledged restraint, but in January 1917 Germany decided that victory was within reach if its U-boats could cut the supply lines between the Allies and the United States. Anticipating that the United States was likely to declare war once unrestricted submarine warfare resumed, the German foreign minister, Arthur Zimmermann, took a gamble and tried to secretly entice Mexico into attacking the United States along their common border. The interception and publication of the Zimmermann Telegram further damaged relations between the United States and Germany. Finally, on April 2, Wilson asked Congress for a declaration of war against Germany, declaring that the “world must be made safe for democracy”. Congress actively debated Wilson’s request, and several legislators, including Senator George W. Norris of Nebraska, voiced doubts about going to war (See Opposition to War). Dissent became harder once the decision for war was made. The United States officially declared war on Germany on April 6, 1917. Entering the war as an “associate” power, the United States cooperated with the Allies but also remained free to pursue its own strategic and foreign policy objectives. Wilson did not request a declaration of war against Austria-Hungary until December, and did so then to prevent Italy from leaving the Allied coalition after catastrophic losses in the Battle of Caporetto. The United States was never at war with the Ottoman Empire or Bulgaria. For classroom-ready, interactive materials, please see our Digital Atlas entry, World War I and the 1920s.