Answer:
War broke out in Europe in the summer of 1914, with the Central Powers led by Germany and Austria-Hungary on one side and the Allied countries led by Britain, France, and Russia on the other. At the start of the war, President Woodrow Wilson declared that the United States would be neutral. However, that neutrality was tested and fiercely debated in the U.S. Submarine warfare in the Atlantic kept tensions high, and Germany’s sinking of the British ocean liner Lusitania on May 7, 1915, killed more than 120 U.S. citizens and provoked outrage in the U.S. In 1917, Germany’s attacks on American ships and its attempts to meddle in U.S.-Mexican relations drew the U.S. into the war on the side of the Allies. The United States declared war on Germany on April 6, 1917.