Rabaul's open approaches gave Japanese convoys room to maneuver

Operation Cartwheel advanced through the Southwest Pacific toward New Britain and Rabaul, a center of Japanese operations and logistics. Rabaul's broad ocean approaches allowed convoys more room to maneuver around submarine threats. Singapore's confined approaches offered fewer route choices to ships facing Allied submarines operating from the Indian Ocean and Australia. The wartime avoidance of major English Channel convoy routes provides a comparison: narrow waters made shipping movements more predictable and concentrated the threat. Rabaul consequently held particular importance for Japanese operations in this region. Both the Japanese Army and Navy recognized the need to defend it, although agreement on its importance did not establish effective coordination.