Embarking for Singapore on 2 February 1941 from Darling Harbour on the ocean liner "Queen Mary", the battalion arriving at the naval dock in Singapore. Upon arrival, the 2/20th were moved by train to Bagan Pinang and from there marched to Port Dickson, in south-west Malaya where it conducted further training. In early August, Lieutenant Colonel Charles Assheton took over as commanding officer, and the battalion was redeployed to Mersing, constructing defences there. Following the landings on 8 December 1941, the battalion was subsequently involved in fighting against the Japanese as part of the Malayan campaign. The first strikes of the Japanese attack fell on British and Indian troops in the north of the country, and initially the Australian units, which were based in primarily in the south around Johore, did not see much fighting. On 7 January 1942, C Company was detached to form part of a special unit to delay the Japanese advance at Endau on the north coast, clashing with the Japanese on a number of occasions before withdrawing to the battalion main defensive position at Mersing on 26 January. Meanwhile, the remainder of the battalion at Mersing also clashed with the Japanese on a number of occasions, and was heavily bombed. After being rejoined by C Company, the 2/20th Battalion withdrew to Singapore Island on 31 January, where it took up positions on the northern flank of the brigade sector. In the week following the withdrawal from Malaya, the battalion received an influx of about 80 reinforcements, who were largely untrained having been shipped hastily from Australia with little regard to their preparedness, to make up for earlier losses.