While historians believe that after the victory at Midway Island the course of the war in the Pacific was set, this excellent history of the naval battels around Guadalcanal shows that had the U.S. navy not prevailed, the marines on the island would have been defeated, displayed in captivity and a serious setback handed to the overall strategy.  That the U.S. naval forces were not defeated was not due to the brilliance of the naval leadership, but rather due to luck, a technological advantage that was nearly thrown away, sheer luck and the misunderstanding of the Japanese military which was focused on tactics instead of logistics.