 American Republic P-47 Thunderbolts and Lockheed P-38 Lightnings from the 348th and 475th Fighter Groups were also used to provide fighter cover for Allied shipping, while heavy and medium bombers from the Fifth Air Force carried out strategic bombing missions to reduce Japanese airbases around Wewak and New Britain, and raided Japanese lines of communication in concert with PT boats.Due to the impracticalities of using wheeled transport in the jungle, Allied logistics was undertaken primarily by means of water transport such as landing craft and barges which moved supplies along the coast, with overland supply to combat units being completed by New Guinean labourers and, at times, by Australian combat troops themselves, which were re-roled temporarily to undertake portage tasks as required, and augmented where possible with jeeps.The main Japanese force in the campaign was provided by the XVIII Army under the command of Lieutenant General Hatazō Adachi and was headquartered at Madang.