United States joins the fight

In January 1917, the Germans announced that their submarines would sink without warning any ship in the waters around Britain. This policy was called unrestricted submarine warfare. The Germans had tried this policy before where a German submarine sank the British passenger ship Lusitania which included 128 U.S. citizens. Germany claimed that the ship had been carrying ammunition, which turned out to be true. President Woodrow Wilson sent a strong protest to Germany. After two further attacks, the Germans finally agreed to stop attacking neutral and passenger ships. Desperate for an advantage over the Allies, however, the Germans returned to unrestricted submarine warfare in 1917. They knew it might lead to war with the United States. Ignoring warnings by President Wilson, German U-boats sank three American ships. Also, Officials intercepted a telegram written by Germany’s foreign secretary, Arthur Zimmermann, stating that Germany would help Mexico “reconquer” the land it had lost to the United States if Mexico would ally itself with Germany. Also, America felt a bond with England. The two nations shared a common ancestry and language, as well as similar democratic institutions and legal systems. More important, America’s economic ties with the Allies were far stronger than those with the Central Powers. On April 2, 1917, President Wilson asked Congress to declare war on Germany. The United States entered the war on the side of the Allies.