Before the Japanese invasion of Malaya, the Japanese…
The Japanese were initially resisted by III Corps of the Indian Army and several British Army battalions. The Japanese quickly isolated individual Indian units defending the coastline, before concentrating their forces to surround the defenders and forcing their surrender.The defeat of Allied troops at Jitra by Japanese forces, supported by tanks moving south from Thailand on 11 December 1941 and the rapid advance of the Japanese inland from their Kota Bharu beachhead on the north-east coast of Malaya overwhelmed the northern defences. Without any real naval presence, the British were unable to challenge Japanese naval operations off the Malayan coast, operations which proved invaluable to the invading army. With virtually no remaining Allied planes, the Japanese also had mastery of the skies, leaving the Allied ground troops and civilian population exposed to air attack.
The Malayan island of Penang was bombed daily by the Japanese from 8 December and abandoned on 17 December. Arms, boats, supplies and a working radio station were left in haste to the Japanese. The evacuation of Europeans from Penang, with local inhabitants being left to the mercy of the Japanese, caused much embarrassment for the British and alienated them from the local population. Historians judge that "the moral collapse of British rule in Southeast Asia came not at Singapore, but at Penang"
On 23 December, Major-General David Murray-Lyon of the Indian 11th Infantry Division was removed from command to little effect. By the end of the first week in January, the entire northern region of Malaya had been lost to the Japanese. At the same time, Thailand officially signed a Treaty of Friendship with Imperial Japan, which completed the formation of their loose military alliance. Thailand was then allowed by the Japanese to resume sovereignty over several sultanates in northern Malaya, thus consolidating their occupation. It did not take long for the Japanese army's next objective, the city of Kuala Lumpur, to fall. The Japanese entered and occupied the city unopposed on 11 January 1942. Singapore Island was now less than 200 mi (320 km) away for the invading Japanese army.
The 11th Indian Division managed to delay the Japanese advance at Kampar for a few days, in which the Japanese suffered severe casualties in terrain that did not allow them to use their tanks or their air superiority to defeat the British. The 11th Indian Division was forced to retreat when the Japanese landed troops by sea south of the Kampar position. The British retreated to prepared positions at Slim River.
At the disastrous Slim River battle, in which two Indian brigades were practically annihilated, the Japanese used surprise and tanks to devastating effect in a risky night attack. The success of this attack forced Percival into replacing the 11th Indian Division with the 8th Australian Division.
Defence of Johor: Battle of Muar
By mid-January, the Japanese had reached the southern Malayan state of Johore where, on 14 January, they encountered troops from the Australian 8th Division, commanded by Major-General Gordon Bennett, for the first time in the campaign. During engagements with the Australians, the Japanese experienced their first major tactical setback, due to the stubborn resistance put up by the Australians at Gemas. The battle—centred around the Gemencheh Bridge—proved costly for the Japanese, who suffered up to 600 casualties but the bridge itself—which had been demolished during the fighting was repaired within six hours.
As the Japanese attempted to outflank the Australians to the west of Gemas, one of the bloodiest battles of the campaign began on 15 January on the peninsula's West coast near the Muar River. Bennett allocated the 45th Indian Brigade—a new and half-trained formation—to defend the river's South bank but the unit was outflanked by Japanese units landing from the sea and the Brigade was effectively destroyed with its commander, Brigadier H. C. Duncan, and all three of his battalion commanders killed.
Two Australian infantry battalions—which had been sent to support the 45th Brigade were also outflanked and their retreat cut off, with one of the Australian battalion commanders killed in the fighting around the town of Bakri, south-east of Muar. During the fighting at Bakri Australian anti-tank gunners had destroyed nine Japanese tanks, slowing the Japanese advance long enough for the surviving elements of the five battalions to attempt an escape from the Muar area.
Led by Australian Lieutenant-Colonel Charles Anderson, the surviving Indian and Australian troops formed the "Muar Force" and fought a desperate four-day withdrawal, allowing remnants of the Commonwealth troops withdrawing from northern Malaya to avoid being cut off and to push past the Japanese to safety. When the Muar Force reached the bridge at Parit Sulong and found it to be firmly in enemy hands, Anderson, with mounting numbers of dead and wounded, ordered "every man for himself". Those that could took to the jungles, swamps and rubber plantations in search of their division headquarters at Yong Peng. The wounded were left to the mercy of the Japanese and all but two out of 135 were tortured and killed in the Parit Sulong Massacre. Anderson was awarded a Victoria Cross for his fighting withdrawal. The Battle of Muar cost the allies an estimated 3,000 casualties including one brigadier and four battalion commanders.
On 20 January, further Japanese landings took place at Endau, in spite of an air attack by Vildebeest bombers. The final Commonwealth defensive line in Johore of Batu Pahat-Kluang-Mersing was now being attacked along its full length. Unfortunately, Percival had resisted the construction of fixed defences in Johore, as on the North shore of Singapore, dismissing them in the face of repeated requests to start construction from his Chief Engineer, Brigadier Ivan Simson, with the comment "Defences are bad for morale." On 27 January, Percival received permission from the commander of the American-British-Dutch-Australian Command—General Archibald Wavell—to order a retreat across the Johore Strait to the island of Singapore.