On June 7, 1943, the 204th Air Group at Buin base planned an operation to bomb Allied Russell Islands airfield with 81 fighters. Twelve Zeros, armed with firebombs beneath each wing, in 3 sets of “Lotte” formations approached at an altitude of 8000 m, while other Zero groups escorted. The reinforced 50 Allied fighters adopted new formation tactics with 10 fighters in 1 group each. A furious battle resulted between the Zeros and the 50 Allied fighters. Over the airfield, Yanagiya's group dived from 8,000 m (26,000 ft) to 6,000 m (20,000 ft), released their firebombs then pulled up.