MacArthur now bypassed the Japanese forces at Hansa Bay and Wewak, and assaulted Hollandia and Aitape, which Willoughby reported to be lightly defended. Although they were out of range of the Fifth Air Force's fighters based in the Ramu Valley, the timing of the operation allowed the aircraft carriers of the Pacific Fleet to provide air support. Though risky, the operation turned out to be a brilliant success. MacArthur caught the Japanese off balance and cut off Lieutenant General Hatazō Adachi's Japanese XVIII Army in the Wewak area. Because the Japanese were not expecting an attack, the garrison was weak, and Allied casualties were correspondingly light. However, the terrain turned out to be less suitable for airbase development than first thought, forcing MacArthur to seek better locations further west. Moreover, while bypassing Japanese forces had great tactical merit, it had the serious strategic drawback of tying up large numbers of Allied troops in order to contain them, and Adachi was far from beaten. In the Battle of Driniumor River, he would bring on "the New Guinea campaign's bloodiest and most strategically useless battle."