American ships became targets of attack by 1917 because Americans refused to take sides in the war. Americans used their ships to spy on the Germans. Americans continued to trade with the warring nations. Americans insisted on protecting their citizens at sea.

For two and a half years, then-US President Woodrow Wilson had managed to weave a delicate political balance to keep the country out of the European conflict, often facing intense internal political opposition. Wilson was a reserved and severe intellectual, a descendant of Scottish Presbyterians. His traumatic experience as a child of a southern state during the American Civil War led him to decide that the country should be left out of the European conflict when it began, in 1914.

On April 2 Wilson spoke before Congress. With a deep sense of the solemn and tragic step he was taking, he told the parliamentarians that they should consider the German actions as a declaration of war against the government and the people of the United States. Armed neutrality had proved ineffective, since it was impossible to implement to defend the ships against the attacks of German submarines.