only 164 first-line aircraft in Malaya and Singapore and the only fighter type was the sub-standard Brewster 339E Buffalo. The Buffaloes were operated by one Royal New Zealand Air Force (RNZAF), two Royal Australian Air Force (RAAF), and two Royal Air Force (RAF) squadrons. The aircraft were, according to historian Peter Dennis, "not considered good enough for use in Europe" and major shortcomings included a slow rate of climb and the fuel system, which required the pilot to hand-pump fuel if flying above . The Imperial Japanese Army Air Force was more numerous and better trained than the second-hand assortment of untrained pilots and inferior Commonwealth equipment remaining in Malaya, Borneo and Singapore. Japanese fighters were superior to the Commonwealth fighters, which helped the Japanese to gain air supremacy. Although outnumbered and outclassed, the Buffalos were able to provide some resistance, with RAAF pilots alone managing to shoot down at least 20 Japanese aircraft before the few survivors were withdrawn. Force Z, consisting of the battleship , the battlecruiser and four destroyers, sailed north out of Singapore on 8 December to oppose expected Japanese landings along the coast of Malaya. Japanese land-based aircraft found and sank the two capital ships on 10 December, leaving the east coast of the Malayan Peninsula exposed and allowing the Japanese to continue their amphibious landings. Japanese forces quickly isolated, surrounded and forced the surrender of Indian units defending the coast. Despite their numerical inferiority, they advanced down the Malayan Peninsula, overwhelming the defences. The Japanese forces also used bicycle infantry and light tanks, allowing swift movement through the jungle. The Commonwealth having thought the terrain made them impractical, had no tanks and only a few armoured vehicles, which put them at a severe disadvantage. Although more Commonwealth units—including some from the 8th Australian Division—joined the campaign, the Japanese prevented them from regrouping. The Japanese overran cities and advanced toward Singapore, which was an anchor for the operations of the American-British-Dutch-Australian Command (ABDACOM), the first Allied joint command of the Second World War. Singapore controlled the main shipping channel between the Indian and the Pacific Oceans. An ambush was sprung by the 2/30th Australian Battalion on the main road at the Gemenceh River near Gemas on 14 January, causing many Japanese casualties. At Bakri, from 18 to 22 January, the Australian 2/19th and 2/29th battalions and the 45th Indian Brigade (Lieutenant Colonel Charles Anderson) repeatedly