The attack on Pearl Harbor and the subsequent German declaration of war on the United States had an immediate effect on the campaign. Dönitz promptly planned to attack shipping off the American East Coast. He had only 12 Type IX boats able to reach US waters; half of them had been diverted by Hitler to the Mediterranean. One of the remainder was under repair, leaving only five boats for Operation Drumbeat ("Paukenschlag"), sometimes called by the Germans the "Second happy time."