initially so successful that this became known among U-boat crews as the second happy time. Eventually, the institution of shore blackouts and an interlocking convoy system resulted in a drop in attacks and U-boats shifted their operations back to the mid-Atlantic. The turning point of the Battle of the Atlantic took place in early 1943 as the Allies refined their naval tactics, effectively making use of new technology to counter the U-boats. The Allies produced ships faster than they were sunk, and lost fewer ships by adopting the convoy system. Improved anti-submarine warfare meant that the life expectancy of a typical U-boat crew would be measured in months. The vastly improved Type 21 U-boat appeared as the war was ending, but too late to affect the outcome. In December 1943, the last major sea battle between the Royal Navy and Nazi Germany's Kriegsmarine took place. At the Battle of North Cape, the German battleship , was sunk by , , and several destroyers. Pacific War The Pacific War was the part of World War II, especially following the successful Japanese attack on United States forces at Pearl Harbor to 1945. The main American naval theaters were as Pacific Ocean Areas and Southwest Pacific Area. The British fought chiefly in the Indian Ocean. It was a war of logistics, with American home bases in California and Hawaii sending supplies to Australia. The U.S. used its submarines to sink Japanese transports and oil tankers, thereby cutting off Japan's supplies to its outposts and causing a severe shortage of gasoline. Island hopping was the key strategy to bypass heavily fortified Japanese positions and instead concentrate the limited Allied resources on strategically important islands that were not well defended but capable of supporting the drive to the main islands of Japan. This strategy was possible in part because the Allies used submarine and air attacks to blockade and isolate Japanese bases, weakening their garrisons and reducing the Japanese ability to resupply and reinforce. Most Japanese soldiers killed in the Pacific died of starvation, and Japan used its submarine fleet to try to resupply them. Hard-fought battles on the Japanese home islands of Iwo Jima, Okinawa, and others resulted in horrific casualties on both sides, but finally produced a Japanese retreat. Faced with the loss of most of their experienced pilots, the Japanese increased their use of kamikaze tactics in an attempt to create unacceptably