Following the outbreak of the war with Japan, 51 Hurricane Mk IIBs en route to Iraq were diverted to Singapore; 10 were in crates, the others partially disassembled, these and the 24 pilots (many of whom were veterans of the Battle of Britain), who had been transferred to the theatre, formed the nucleus of five squadrons. They arrived on 13 January 1942, by which time the Allied fighter squadrons in Singapore, flying Brewster Buffalos, had been overwhelmed during the Malayan campaign. The fighters of the Imperial Japanese Army Air Force, especially the Nakajima Ki-43 Oscar, had been underestimated in its capability, numbers and the strategy of its commanders.