Geographically part of the Solomon Islands, but administratively part of the Territory of New Guinea at the time of the battle, Bougainville lies at the northeastern end of the Solomon Islands chain. Roughly shaped like a fiddle, the island is long and, at its widest point, across. It is dominated by thick jungle and large mountain peaks in its interior, with narrow beaches around the west coast. Situated south-east of New Britain, Bougainville offered the Allies another step in their advance through the Solomons towards the main Japanese base that had been established around Rabaul. The reduction and isolation of this base was a key Allied objective of the Operation Cartwheel. Seizure of Bougainville offered the Allies the ability to establish forward airfields from which to launch attacks against Rabaul, as well as anchorages around Empress Augusta Bay and Soraken, which could be utilized for Allied shipping.