 The Japanese 143 Infantry Regiment (from 55th Division) then launched overland attacks on the airfields at Tavoy and Mergui in Tenasserim.The airfields were difficult to defend and reinforce, but Burma Army HQ had been ordered to hold these outposts because of their importance to the defence of Malaya.The Japanese forced their way over the steep jungle-covered Tenasserim Range, and attacked Tavoy on 18 January.