The Imperial Japanese Army (IJA) believed that holding the Solomon Islands would be ultimately unsuccessful and that it would be better to wait for an Allied attack on Bougainville which would be much less costly to supply and reinforce. The Imperial Japanese Navy (IJN) preferred to delay the Allied advance for as long as possible by maintaining a distant line of defense. With no effective central command, the two Japanese services implemented their own plans: the navy assumed responsibility for the defense of the central Solomons and the army for the northern Solomons.