Germany’s resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson’s decision to lead the United States into World War I. Following the sinking of an unarmed French boat, the Sussex, in the English Channel in March 1916, Wilson threatened to sever diplomatic relations with Germany unless the German Government refrained from attacking all passenger ships and allowed the crews of enemy merchant vessels to abandon their ships prior to any attack. On May 4, 1916, the German Government accepted these terms and conditions in what came to be known as the “Sussex pledge.”
