Following the outbreak of war in the Pacific in December 1941, the 2/18th saw action against Japanese forces in the Malayan campaign, during which they took part in a large-scale ambush of a Japanese force on the Malay Peninsula before joining the withdrawal to Singapore in early 1942. Assigned to defend part of the north-west coast of the island, the battalion participated in the unsuccessful defence of Singapore in early February 1942. Following the fall of Singapore the majority of the battalion's personnel were taken as prisoners of war. Many of these men died in captivity; the survivors were liberated in 1945 and returned to Australia where the battalion was disbanded.