Covered in sweat, and emerging from his Type 97 Medium Tank, Lieutenant Watanabe of the Imperial Japanese Army must have been surprised. Here he stood, at the Trolak bridge. Three hours ago it had been defended by a British Brigade. Now the British Brigade was destroyed, the entire British division and its defence on this axis had been unhinged and the road to Kuala Lumpur was open. It wasn’t supposed to be this easy. As Lieutenant Watanabe dismounted, the sound of fighting must have been close at hand. The young Troop Leader quickly realised the Trolak Bridge had been wired for reserve demolitions. He strode forward, drew his samurai sword and brought it down on the wires, saving the bridge from destruction. He quickly remounted his vehicle. Momentum was with him. The British were on the back foot. He would press home the attack into the next Brigade…

A Shock Action Case Study

The Battle of Slim River presents an excellent opportunity to examine the role of shock action in war. This article will use the experiences gained on the 2018 Australian Army Research Centre Staff Ride of Malaysia and Singapore conducted over 06-16 May 2018 to provide an understanding of the battle. This will allow the importance of shock action to be explained, a definition explored and to suggest a method to understand and employ shock action.

The Battle of Slim River

Arguably the decisive action of the Japanese invasion of Malaya and Singapore, the Battle of Slim River occurred on the 7^thof January 1942. Just 30 days earlier, a Japanese invasion force under the command of Colonel Ando had landed in Southern Thailand. Narrow mobility corridors through the mountainous jungle terrain of Malaya constrained the Japanese forces’ prospects for seizing Fortress Singapore, 600 kilometres to their south. Yet despite this substantial obstacle, the Japanese moved quickly. British planners had expected to defend these mobility corridors with well-sited, division-sized defences; however, by means of shallow envelopments and rapidly-garnered momentum, the Japanese proved adept at routing large British formations.

With the British on the back foot and after a series of significant withdrawals, the fatigued Indian 11th Division found themselves at Slim River. The waterway represented the most significant obstacle to the Japanese advance on the Western coast of Malaya. Adapting to the Japanese tactics, the British division arrayed itself in depth along the road crossing Slim River. This would make further envelopments difficult and force the Japanese to fight on the road.

After initial probing attacks had identified the forward edge of this new British position near Slim River, the Japanese advanced guard commander sought to again turn the flanks of the British position. Instead, Major Shimada, the commander of a Japanese tank unit, strongly advocated for a penetration on axis led by armour. Colonel Ando agreed, and at 0330 h on the 7^thof January 1942, a combined arms team consisting of 30 tanks, mounted infantry, and engineers, supported by light artillery, commenced their attack.

Forced to attack on a very narrow frontage, Major Shimada sought to achieve a rapid penetration in order to exploit their attack into unprepared rear areas. Using the low light of the early morning, supported by light guns that suppressed the forward British company, Japanese engineers moved forward and cleared the most significant obstacles on the main road. Major Shimada’s lead tank platoon, led by Lieutenant Watanabe, then broke into the first position. Poorly-laid obstacles and unprepared anti-tank guns allowed ground troops to guide vehicles through the remainder of the road block and the attack to achieve immediate success.

Capitalising on the momentum gained from this first contact, the armoured column rapidly assaulted subsequent companies of the 4^th/19^thHyderabad Battalion, using immediate bypass routes for any obstacles en route to retain the initiative. By 0630, the Japanese attack had captured the Trolak bridge intact and an entire British Brigade had been routed. Over the next two hours, the Japanese column would destroy a second Brigade, deploying machine gun fire to scythe down entire companies still in marching order and allowing the Japanese to capture their final objective, the Bridge over the Slim River.

The penetration was only stopped when a British battery of 25 pounder artillery, engaging with direct fire over open sights, was able to establish an effective block.

At this point, the entire British division’s defence had been unhinged. The Japanese penetration had secured the key bridges, routing any significant defences on route and allowing the main body of the Japanese 41^st Infantry Regiment to advance in the wake of the attack and mop up any remaining resistance. The British would accede the next 300 kilometres of ground to the Japanese advance without a fight: the fate of the British in Malaya was sealed.

Yet a conventional understanding of the initial situation at Slim River would suggest the British should have been able to achieve considerable delay upon the Japanese, luring them into a battle of attrition. Instead, the Japanese conducted a decisive manoeuvre that destroyed British cohesion and left them vulnerable to exploitation by the rapid successive actions of Japanese forces. This Japanese victory can thus be attributed to shock action.