At the outbreak of the war, the United States pursued a policy of non-intervention: avoiding conflict while trying to broker peace. When the German U-boat "U-20" sank the British liner RMS "Lusitania" on 7May 1915 with 128 Americans among the dead, President Woodrow Wilson insisted that America is "too proud to fight" but demanded an end to attacks on passenger ships. Germany complied. Wilson unsuccessfully tried to mediate a settlement. However, he also repeatedly warned that the United States would not tolerate unrestricted submarine warfare, in violation of international law. Former president Theodore Roosevelt denounced German acts as "piracy". Wilson was narrowly re-elected in 1916 after campaigning with the slogan "he kept us out of war".