During the First World War, America did not take part since the beginning. Woodrow Wilson urged the American nation to remain neutral in the war. But Americans began to favor allies because of propaganda, and the use of biased information by the Allies to change the attitudes of public opinion and achieve a political goal. For this purpose, the British cut the trans Atlantic telegraph, so the Americans could hear only the British side. Many Americans had investments and connections to England.
The Germans, on the other hand, threatened to sink every ship in the British waters. So they sank the Lusitania ship carrying American and British travelers. On this occasion Senator works said that if the German government should make aggressive warfare against the U.S. war against Germany would be justified.
But it was not justified by sinking a few civilian ships.