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 who 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. In the face of repeated requests from his Chief Engineer, Brigadier Ivan Simson, Percival had resisted the construction of fixed defences in Johore, as on the North shore of Singapore, dismissing them 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. Retreat to Singapore On 31 January, the last organised Allied forces left Malaya, and Allied engineers blew a -wide hole in the causeway that linked Johore and Singapore; a few stragglers would wade across over the next few days. Japanese raiders and infiltrators, often disguised as Singaporean civilians, began to cross the Straits of Johor in inflatable boats soon afterwards. In less than two months, the Battle for Malaya had ended in comprehensive defeat for the Commonwealth forces and their retreat from the Malay Peninsula to the fortress of Singapore. Nearly 50,000 Commonwealth troops had been captured or killed during the battle. The Japanese Army invaded the island