Period: December 7, 1941
Quote: Winston Churchill: The only thing that ever really frightened me during the war was the U-boat peril.
After Germany had failed in the Battle of Britain in late 1940, it was important for the German army to disrupt the British supply of military equipment and other goods from the United States. To achieve this, the Germans employed submarines.
The German U-boats came into direct contact with the neutral US Army fleet that accompanied and defended the British supply convoys. Due to their neutrality the US ships should not have come under attack by the Germans, but there were some skirmishes.
After December 7, 1941, the day of the Japanese attack on Pearl Harbor, the war between Japan and the United States was announced. On 9 December Hitler gave the order for German submarines to attack the US fleet. The United States was now fully involved in the war.
The Battle of the Atlantic was an entirely new phase: disabling German submarines was now a top priority for the Allies. During 1942, attacks by German U-boats resulted in huge numbers of casualties, but from 1943 the tide turned: new technologies (sonar) made it possible to detect the submarines underwater. In addition the German Enigma codes of their military communications was cracked. Also the US production of shipping was at full capacity, and every month more new ships were being produced than the Germans were sinking.
Nevertheless, German submarines continued to be a danger until the end of the war. All American soldiers were brought to Europe by boat from America and would have had to deal with the threat of a well-aimed German torpedo.