A Division contains 10,000-15,000 soldiers. Even if we consider the division is undermanned and lost men due to previous engagements and attrition, there is no way the British put less than 7000 soldiers at Slim River. And note that the British had sufficient warning and prepared their defences considerably strong enough to halt the Japanese advance. Or did they? Going by the fact that there are very few battles Britain won due to their excellent generalship facing an equal, or even an inferior, one will surely pause and think what exactly happened in the Malaya and Singapore Campaign. Japan, with less than half the army Britain held completely occupied Malaya and Singapore in less than three months. While the British expected Singapore to hold out for at least 3-6 months, it was taken in 15 days. Is it because of the quality of the leadership and their vintage ideas, incapable of comprehending the changing trends of war?
Nothing can be more apt to talk about the incompetency of the British military command than their conduct in the Battle of Slim River.
On 2 Jan 1942, forces of Indian 11th Infantry Division started retreating to Trolak. There were probing attacks on 6 Jan 1942 at Trolak but were beaten down. The actual battle started at 3:30 AM the next day and the complete division was on run by noon, this, going by the fact that the road is a narrow one, with thick foilage on either side, forcing the Japanese to follow the road till it’s end – a very good opportunity for the British to destroy the Japanese had they planned properly/had they been led by a competent leader. At one point, Japanese tanks were stuck in a single file giving a perfect opportunity for the British, which they didn’t utilize. Well,…
The course of action is below –

Start End Britain Commander Status Japan losses British reported to duty
3:30 am 4:00 am 4/19th Hyderabad Regiment Alan Davidson Brown Unit dismembered and scattered 1 tank
4:30 am 6:00 am 5/2nd Punjab Regiment Cecil Deakin Unit dismembered and scattered 3 tanks
6:30 am 7:30 am 2nd Battalion, Argyll and Sutherland Highlanders Lindsay Robertson Unit dismembered and scattered 0 tanks 94
7:30 am 8:00 am 5/14th Punjabi Regiment Cyril Stokes Machine Gunned while marching – unit dismembered and scattered 0 tanks 146
8:00 am Sirmoor Rifles & 2/9th Gurkhas(28th Brigade) Units withdrew, Headquarters falls 0 tanks
2/1st Gurkha Regiment Jack Oswald Fulton Machine Gunned while marching – unit dismembered and scattered 0 tanks 28
8:30 am Bridges Over River Slim taken

It is pertinent to note that a regiment contains around 2000 soliders and a brigade, 1000. We are staring at an army of a minimum strength 7-8000 soldiers in a very advantageous geography, who were all but brushed aside in a matter of five hours and 25 km of dangerous stretch taken. This, going by the fact that the whole division was scattered with just a single Japanese regiment with the support of 100 tanks and no air cover. Well, the division head, Archibald Paris was sacked after this defeat, even though he was considered one of the best British field commanders available in Malaya.