At the outbreak of fighting in 1914, the United States remained on the sidelines of World War I, adopting the policy of neutrality favored by President Woodrow Wilson while continuing to engage in commerce and shipping with European countries on both sides of the conflict. Neutrality, however, was increasingly difficult to maintain in the face of Germany's unchecked submarine aggression against neutral ships, including those carrying passengers. In 1915, Germany declared the waters surrounding the British Isles to be a war zone, and German U-boats sunk several commercial and passenger vessels, including some U.S. ships. Widespread protest over the sinking by U-boat of the British ocean liner Lusitania-traveling from New York to Liverpool, England with hundreds of American passengers onboard--in May 1915 helped turn the tide of American public opinion against Germany. In February 1917, Congress passed a $250 million arms appropriations bill intended to make the United States ready for war. Germany sunk four more U.S. merchant ships the following month, and on April 2 Woodrow Wilson appeared before Congress and called for a declaration of war against Germany.