The great majority of the Japanese aircraft engaged by the Cactus Air Force during its history were from Imperial Japanese Navy air units. On 7 August, when the Guadalcanal campaign began, the 5th Air Attack Force, under Rear Admiral Sadayoshi Yamada, operated from Rabaul, New Britain, and Lae, Papua New Guinea, and was responsible for naval air operations in eastern New Guinea and the Solomon Islands. The 5th was a hybrid organization composed mainly of attached units from the 25th Air Flotilla and reported to the 11th Air Fleet (also called the "Base Air Force"), under Nishizo Tsukahara. On the morning of 7 August, the 5th's air strength consisted of 39 fighters, 32 medium bombers, 16 dive bombers, and 17 seaplanes, including the 15 seaplane aircraft at Tulagi that were destroyed in the initial Allied air strikes during the landings on Tulagi and Guadalcanal.