When the Japanese attacked Pearl Harbor on 7 December 1941, they had already sent an invasion force to attack the British forces based in Malaya. Murray-Lyon's 11th Indian Division was based in the north of Malaya, focused on the border with Thailand. Although the British Army in Malaya was expecting the Japanese invasion and had even prepared defences and plans for counterattacks, they still were overconfident and massively ill-prepared to face the highly disciplined, organised and battle experienced Japanese Army. Murray-Lyon's division looked good on paper, but in reality it consisted of two regular British Army battalions (The Leicestershire Regiment and the East Surrey Regiment), the backbone of the division, four newly raised and half-trained Indian Army battalions and three Gurkha battalions, one of which consisted of 18-year-olds who had only recently arrived in Malaya. There were no tanks in the entire peninsula and a chronic shortage of aircraft. With this Murray-Lyon faced the Japanese attacks that came through southern Thailand in early December 1941.