 With the start of hostilities against the United States, the 4th Fleet was based out of Truk, with a secondary base at Kwajalein.After initial Japanese successes, additional bases were established in the southern Philippines, Guam, Wake Island, Gilbert Islands, eastern New Guinea, Bismarck Archipelago and the Solomon Islands.After the Battle of the Coral Sea, the area covered by the 4th Fleet was reduced to an “inner core” of Japanese possessions, while the new IJN 8th Fleet was assigned to confront the advancing American forces in the Solomon Islands and New Guinea.