The Battle of Slim River occurred during the Malayan campaign in January 1942 between the Imperial Japanese Army and the British Indian Army on the west coast of Malaya.
Background
Japanese forces had invaded north-west Malaya from southern Thailand on 11 December 1941 and eastern Malaya on 7 December at Kota Bharu. From Thailand they had driven relentlessly down the western coast of Malaya defeating all British attempts at stopping them. By Christmas Day the Japanese held all of north-west Malaya. One of the few moments where British troops managed to inflict any form of effective defense against Japanese tactics occurred near Kampar on the Dipang River. At the Battle of Kampar, in a four-day battle notable for the effectiveness of the British artillery, the Japanese suffered heavy casualties. By 2 January, though, the Indian 11th Infantry Division was out flanked by seaborne landings south of the Kampar position, out numbered and with Japanese forces attempting to cut the division off from the road to Singapore, they withdrew to prepared positions at Trolak five miles north of the Slim River.
British positions at Trolak
The defenses on the road to Trolak started with a four-mile corridor at the 60 mile post extending through almost impenetrable jungle to the 64 mile post, after the village the road cuts through the more open terrain of the Cluny Rubber estate for five miles before reaching the Slim River rail bridge. The road then bends east and follows the river upstream for another six miles before it crosses the Slim River at a road bridge. The British commander, Acting Major-General Paris (normally commander of the 12th Indian Infantry Brigade), had lost one of his three brigades after the fighting at Kampar; the amalgamated 5/16 Brigade, after retreating through the 12th Brigade, had been moved to a coastal defense position further south to defend the western flank of the division and to rest and reorganise. This left Paris with Lt.Col.Ian Stewart's 12th Indian Brigade and Lt.Col.Ray Selby's 28th Gurkha Brigade, both at reduced strengths due to heavy casualties in the earlier battles at Kampar and on the Grik Road, to defend the northern bank of the river.
Stewart's battalions were in a line straddling either side of the road and spreading back through the thick jungle part of the corridor to north of Trolak where the Cluny Rubber estate started and where Stewart placed his Headquarters. The 4/19th Hyderabad Regiment held the forward position with anti-tank obstacles and road blocks. The next and last prepared positions were held by the 5/2nd Punjab Regiment. The 2nd Argyll and Sutherland Highlanders were grouped in a defensive position but without fixed anti-tank obstacles or road blocks. Selby's Gurkhas were spread along the road and railway leading up to both bridges, which had been prepared for demolition.
The Japanese attacking force
The Japanese attacking force came from Colonel Ando's battle group (mainly from the 42nd Infantry Regiment) which had taken over from the chastened Okabe Regiment (41st Infantry Regiment) which had suffered heavy casualties in the artillery ambush at Kampar, both units were from the 5th Division . The assault force consisted of about 17 Type 97 medium tanks and 3 Type 95 Ha-Go Light Tanks, under the command of Major Toyosaku Shimada (:ja:島田豊作). Shimada came up with the plan, unusual in World War II, of a night attack using tanks to spearhead the infantry, a dangerous proposition for tanks considering the extremely low visibility factor which would hamper their crews.
Battle
On the afternoon of 5 January 1942 the rearguard from the 5th/16th Brigade withdrew through the 12th Brigade positions. Soon afterwards the advance guard from Colonel Ando's 42nd Regiment reached the Hyderabad positions and launched a probing attack which was beaten off with the loss of 60 Japanese dead. Ando decided to hold and wait for armor support before launching another attack. On 6 January Major Shimada's tank company arrived and Shimada begged Ando to allow him to attack straight down the road, instead of following the usual Japanese tactics of flanking the British positions.