Japanese Invasion of Malaya (8 December 1941)

The Japanese 25th Army invaded Malaya from Indochina, moving into northern Malaya and Thailand by amphibious assault on 8 December 1941. This was virtually simultaneous with the Japanese attack on Pearl Harbor, which was meant to deter the US from intervening in Southeast Asia. Japanese troops in Thailand coerced the Thai government to let the Japanese use Thai military bases for the invasion of other nations in Southeast Asia and then proceeded overland across the Thai–Malayan border to attack Malaya. At this time, the Japanese began bombing of strategic sites in Singapore, and air raids were conducted on Singapore from 29 December onwards, although anti-aircraft fire kept most of the Japanese bombers from totally devastating the island as long as ammunition was available.
The Japanese 25th Army was resisted in northern Malaya by III Corps of the Indian Army. Although the 25th Army was outnumbered by Allied forces in Malaya and Singapore, Japanese commanders concentrated their forces. The Japanese were superior in close air support, armour, coordination, tactics and experience. Moreover, the British forces repeatedly allowed themselves to be outflanked, believing—despite repeated flanking attacks by the Japanese—that the Malayan jungle was impassable. The Imperial Japanese Army Air Force was more numerous, and better trained than the second-hand assortment of untrained pilots and inferior allied equipment remaining in Malaya, Borneo and Singapore. Their superior fighters—especially the Mitsubishi A6M2 Zero—helped the Japanese to gain air supremacy. The Allies had no tanks and few armoured vehicles, which put them at a severe disadvantage.
The battleship HMS Prince of Wales, the battlecruiser HMS Repulse and four destroyers (Force Z) reached Malaya before the Japanese began their air assaults. This force was thought to be a deterrent to the Japanese. Japanese aircraft, however, sank the capital ships, leaving the east coast of the Malayan peninsula exposed and allowing the Japanese to continue their amphibious landings. Japanese forces quickly isolated, surrounded, and forced the surrender of Indian units defending the coast. They advanced down the Malayan peninsula overwhelming the defences, despite numerical inferiority. The Japanese forces also used bicycle infantry and light tanks allowing swift movement through the jungle.

View of the blown up causeway, with the gap visible in the middle, which delayed Japanese landfall for over a week to 8 February.

Although more Allied units—including some from the Australian 8th Division—joined the campaign, the Japanese prevented the Allied forces from regrouping, overran cities, and advanced toward Singapore. The city was an anchor for the operations of the American-British-Dutch-Australian Command (ABDACOM), the first Allied joint command of the Second World War. Singapore also controlled the main shipping channel between the Indian and the Pacific Oceans. On 31 January, the last Allied forces left Malaya and Allied engineers blew up the causeway linking Johor and Singapore. Japanese infiltrators—many disguised as Singaporean civilians—crossed the Straits of Johor in inflatable boats soon afterwards.

Citation : http://en.wikipedia.org/wiki/Japanese_invasion_of_Malaya