The Japanese attempted to cut off the stream of Allied transports by bombing the Wau airstrip, but it was the rainy season and they were confronted by the same weather conditions which hampered the Allies. Aircraft which did set off from Rabaul were not able to sight the Wau airstrip and returned without accomplishing anything. Not until 6 February was there an aerial engagement. Eight P-39s of the 40th Fighter Squadron were patrolling at over Wau, having provided escort for a flight of five Dakotas, when they sighted 24 Japanese planes. Captain Thomas H. Winburn led his P-39s in an attack, claiming 11 Mitsubishi A6M Zeroes and Mitsubishi Ki-21 "Sallys" shot down. Meanwhile, eight P-40s of the 7th Fighter Squadron also on an escort mission sighted 12 aircraft bombing the airstrip at Wau. The transports they were escorting turned back while the fighters engaged the Japanese, claiming seven aircraft shot down. At this time, there were four Dakotas on the ground at Wau and another five were circling, waiting to land. One Dakota, commanded by Second Lieutenant Robert M. Schwensen, was shot down. All five crewmen on board were killed. A Dakota on the ground was damaged, and a CAC Wirraway was destroyed by a bomb blast. Its two-man crew had hurriedly left the aircraft seconds before and thrown themselves flat on the ground. The pilot, Flight Sergeant A. Rodburn, was unharmed, but the observer, Sergeant A. E. Cole, was hit in the shoulder by shrapnel. The Air Cooperation Signals hut took a direct hit and three men were killed.