 In total, this increase raised the planned output of all merchant shipbuilders to about 500 ships (5 million total deadweight tons) for 1942 and 700 ships (7 million tons) in 1943.The December 7, 1941, Japanese attack on Pearl Harbor and the subsequent entry of the U.S. into the war caused all previously established production schedules to be further revised dramatically upward.With the need to assist Britain in replacing its lost tonnage and to provide adequate ships to the Army to transport troops and supplies to foreign theaters, in January 1942, President Roosevelt asked that 8 million tons of shipping be built in 1942 and 10 million in 1943.