THE UNITED STATES ENTERS WORLD WAR I Timeline 1). 1914 - World War I begins in Europe 2). The United States Remains Neutral 3). Britain’s naval blockade prevents the United States from trading with Germany 4). - Central Powers cannot get the supplies they need - Germany begins submarine warfare (U-Boat attacks) 5). 1915 - Germans sink the British the Brit- ish passenger ship, The Lusitania. 128 Americans were killed in the attack. 6). - Anti-German feelings increase in the U.S. - Wilson warns Germany to stop. - Germany supposed to stop sinking ships with out warning.