The dust was the point. At two fake airfields north of Lae, small Allied construction crews drove trucks in circles to raise visible plumes, and the Japanese obliged by bombing the empty dirt day after day. Fifty miles away at Tsili Tsili, Allied engineers built a real runway in near silence and slipped fighters onto it before anyone noticed. When General George Kenney's Fifth Air Force finally launched its raid on Wewak on 17 August 1943, the American P-38s and B-25s flying escort were close enough to matter. Five days later, the Japanese Fourth Air Army had lost about 170 aircraft and would never again be a serious force over New Guinea.
By August 1943, the Fourth Air Army was already in a bad way. It had been formed two months earlier to defend the New Guinea theater, and on paper it carried 200 aircraft. Only 130 were operational. The Japanese historian Hiroyuki Shindo later wrote that the low readiness rate was caused chiefly by widespread illness among aircrews and the lack of replacement aircraft. Malaria, dengue, and dysentery were eating through the units faster than spare pilots arrived. The four airfields around Wewak, Boram, Dagua, and But held more planes than crews in shape to fly them. The defense relied on visual aircraft spotters rather than radar, which meant incoming raids were detected too late for fighters to scramble. Concealment was inadequate. Hangars were scarce.
On 17 August, 62 B-25s of the Fifth Air Force went in low against Wewak and Boram airfields, each carrying twelve clusters of three 23-pound "parafrag" bombs. The parachutes on the parafrags were the key innovation: they slowed the bombs enough that an attacking aircraft could clear the blast radius at treetop height without being shredded by its own shrapnel. The B-25s strafed and bombed parked aircraft row by row. B-24s of the 90th Bomb Group struck from high altitude. Simultaneously, the 38th Bomb Group hit the airfields at Dagua and But, farther west. Delayed-action bombs cratered the runways so that surviving Japanese aircraft could neither take off nor land. Caught on the ground, the Fourth Air Army had almost no defense to offer.
The price to the Americans was remarkably small. Only three U.S. aircraft were shot down in the raids across all five days, and ten total were lost. One of those losses earned the Medal of Honor. Major Ralph Cheli, commander of the 405th Bombardment Squadron, was leading a low-level attack on Dagua when his B-25 was hit and set on fire. Rather than break formation and climb away to bail out, which would have disrupted the attack run and exposed his squadron to defending fighters, Cheli held formation until after the bomb run before ditching in the water offshore. Cheli and two of his gunners survived the crash and were captured by the Japanese; he was executed at Rabaul on 6 March 1944. The Medal of Honor citation recognized his refusal to abandon the attack and the men depending on his lead.
When the Fourth Air Army counted what it had left, the numbers were staggering. Of roughly 200 aircraft at the four Wewak-area bases, 174 were out of action: 54 shot down, 16 blown up, 57 badly damaged, and 47 slightly damaged. Operational strength collapsed to about 30 planes. This meant a virtual end to Japanese air operations over New Guinea until replacements could arrive, and the replacements never came in force. The Allies could now fly unopposed as far as Aitape, pushing their effective air perimeter more than a hundred miles west. The Fourth Air Army recovered partially but never approached its August 1943 strength. The last major air combat of the New Guinea campaign was fought on 3 June 1944. By the time the last aerial victories were scored that month, the Japanese historian Hiroyuki Shindo notes, the Fourth Air Army had essentially ceased to exist.
Wewak lies at approximately 3.55°S, 143.63°E on the north coast of Papua New Guinea, in East Sepik Province. Wewak Airport (AYWK) occupies the site of the wartime Boram airfield. The old airfields at Dagua and But sit along the coast to the west and can still be identified from the air. Flying from Madang (AYMD) westward along the coast traces roughly the same route as the 1943 American bombers, with the Sepik River plains visible to the south. The region remains lush tropical lowland with heavy afternoon convection; morning flights are smoother. Tsili Tsili, the secret Allied airstrip, was located in the upper Watut Valley inland from Lae.