When Hitler declared war on the United States on December 11th 1941, the Kriegsmarine’s commander of U-boats, Admiral Dönitz, was eager to expand operations to the Western Hemisphere. He saw the entry of the US into the war as a golden opportunity to strike heavy blows in the tonnage war, and he quickly devised plans to launch a devastating campaign that became known as Operation Drumbeat. Dönitz sought Hitler's permission to transfer a dozen long-range Type 9 U-boats from the Mediterranean and launch them against the United States. However, the Führer refused to weaken the German and Italian forces in the Mediterranean, so he only permitted Dönitz to commit six boats to the operation. By December 18, 1941, Dönitz was ready to launch five long-range U-boats for the protracted Atlantic voyage to the U.S. East Coast; one of the six had been withdrawn due to mechanical trouble. The five captains were instructed not to strike ships unless the target weighed more than 10,000 tonnes until they arrived at their designated patrol region, where they would remain on station for two weeks. Dönitz was convinced that the American coastal defences were fragmented and disorganised, and he intended the submarine commanders to employ maximum shock tactics. The five U-boat commanders were to arrive at their respective locations and await Dönitz's final command to launch attacks simultaneously. The admiral determined that this first wave of U-boats would patrol between the St. Lawrence River in Canada and Cape Hatteras on the North Carolina coast. All of Dönitz's U-boats had arrived on station by the evening of January 14, and Operation Drumbeat began.