MacArthur now bypassed the Japanese forces at Hansa Bay and Wewak, and assaulted Hollandia and Aitape, which Willoughby reported to be lightly defended based on intelligence gathered in the Battle of Sio. MacArthur's bold thrust by going 600 miles up the coast had surprised and confused the Japanese high command, who had not anticipated that MacArthur would take such risks. 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 Nimitz's Pacific Fleet to provide air support. Though risky, the operation turned out to be another 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. While bypassing Japanese forces had great tactical merit, it had the strategic drawback of tying up Allied troops to contain them. Moreover, Adachi was far from beaten, which he demonstrated in the Battle of Driniumor River.