On this day in 1917, Imperial Germany announces that it will resume unrestricted submarine warfare. This meant that German submarines would attack all and any ships in the Atlantic that they deemed to be supporting the Allied war effort. The Germans also plainly stated that they were not going to make any allowances for civilian shipping in the Atlantic. The German wanted to destroy any ships in the Atlantic in order to cut off any American supplies that were being shipped to the allies. The Germans hoped by waging unrestricted submarine warfare that they could starve Britain into submission.
The German navy had not been able to contest the Royal Navy’s supremacy at sea. They came to rely on the formidable U-boat. These vessels were usually between 30 and 40 feet long and had a crew of thirty. They were usually armed with a dozen torpedoes. Since 1914 the had sunk thousands of ships.
The Germans had earlier in the war allowed their submarines to attack any ships in the Atlantic. This had resulted in them damaging several American ships. They had later apologized for these and compensated the Americans. The Germans via their embassy warned Americans not to cross the Atlantic, because of the U-boats. On May 7th 1915 the German sank the Lusitania off the southern coast of Ireland and this resulted in the loss of over 1,000 passengers. Over 100 American passengers died on the ship. The Germans maintained that the ship was carrying arms. America was outraged by the sinking of the Lusitania and it seemed that it would lead them to declare war on Germany and the other Central Powers.
This had persuaded the Germans to abandon the use of unrestricted submarine warfare. Their U-boats were ordered only to target ships that belonged to one of the Allied nations. However, this seriously limited the U-boats and they became noticeably less effective. The Germans soon came to realize that they would never starve the British into submission without unrestricted submarine warfare. In January 1917, the Germans announced that they would once again resume unrestricted submarine attacks. This was a gamble and it backfired.
Within hours of their announcement, a German U-boat had attacked an American vessel. No American sailors died in this incident but it caused an uproar in America. Increasingly, many in America believed that war with Germany was inevitable and Congress even began to passed bills for arms appropriations. Not long after the Germans declared the resumption of unrestricted submarine warfare the controversy over the Zimmerman telegram. This was a rather crude attempt by German intelligence to establish an alliance between Berlin and Mexico, in the event of American declaring war on the Central Powers.
The combination of German attacks on US ships and the Zimmerman Telegram persuaded America that they must enter WWI. America declared war on Germany on April 6th 1917.