The correct answer is E) after German U-boats sank four unarmed American merchant vessels.
The United States declared war on Germany after German U-boats sank four unarmed American merchant vessels.
United States President Woodrow Wilson had decided that the best for the US was to maintain the foreign policy of neutrality and to not directly participate in World War I.
However, a couple of international incidents changed Wilson's mind. The United States was drawn into World War because Germany invaded some European territories, the sinking of the Lusitania ship by German U-boats, and the Zimmerman note.
On May 7, 1915, the German Army sank the RS Lusitania, as part of the hostilities during World War I. The sinking was part of the German attack on the British submarine because the British established a naval blockade to the Navy of Germany. This action, the German invasion, and the Zimmerman note, where the Germans promised help to Mexico aid if México supported Germany, were the main reasons why the United States entered World War I.
