In just 10 weeks from 8 December 1941 to mid February 1942, British and Imperial forces were utterly defeated by the numerically inferior Japanese under General Yamashita.
British units fought hard on the Malayan mainland but the Japanese showed greater mobility, cunning and tactical superiority. Morale was badly affected by the loss of HMS Prince of Wales and Repulse to Japanese aircraft on 19 December as they sought out enemy shipping. Panic set in as military and civilians withdrew south to Singapore. Thought to be an impregnable fortress, its defences against land attacks were shockingly deficient. General Percival's leadership was at best uninspired and at worst incompetent.
Once the Allied troops withdrew to Singapore it was only a matter of time before surrender became inevitable. To make matters worse reinforcements arrived but only in time to be made POWs.