North Africa is highly likely to be wrapped up sufficiently early for troops and equipment to be sent to Malaya early enough to make a difference to the fighting. From the end of July Japan is a fairly significant threat and Australia and New Zealand will want something to be done. As soon as their troops are freed up in North Africa they are heading east, to Malaya to prepare for and hopefully deter any Japanese aggression. Why Malaya, that is the front line, and the idea Japan will be able to launch the naval campaign it did won't be considered. As for Britain they will also want to see Japanese aggression deterred, the difference ITTL is they will be able to do something to try and make that happen. No major action in Europe by Britain will be possible for several months at a minimum due to the logistics of preparing for amphibious operations. The Italians can't pull anything major off alone by this stage and the Germans will be a bit distracted in Russia. The only imminent threat is Japan so while Britain is preparing it's next move it may as well do what it can to deter Japan. That means sending Ground, Air and Naval reinforcements.
When looking at the Malayan campaign Britain was deficient in several areas. Several of these are interlinked but in no particular order they are.
- The army units are deficient in equipment in several key areas
- The army units are outnumbered
- The army units are inexperienced
- The Japanese are using tanks, the British aren't.
- The Japanese have air superiority
- The RAF are inexperienced and using poor quality planes.
Now with a sufficiently early finish to the fighting in North Africa, something that is entirely possible suddenly the situation changes quite a lot. Britain will be sending reinforcements to Malaya as a deterrent to the Japanese. Even if this is just the Australian and New Zealand troops it will make a big difference, in addition aircraft will again be sent to try and deter the Japanese.
- The Australian and New Zealand troops will be better equipped even if no British troops are sent (unlikely).
- Those troops sent reduce and perhaps even reverse the Japanese superiority in numbers
- In addition they are also experienced, battle hardened troops by the time they reach Malaya so they stiffen the resolve significantly
- The tank situation may be resolved by directly sending tanks (Matilda I anyone) or offset somewhat by the fact the experienced troops are better able to deal with them.
- Any air assets sent reduce Japanese superiority in numbers and experience so that fight is less one sided.
- Those air assets sent will be experienced again reducing Japanese advantages somewhat though the experience gained fighting German and Italian aircraft is not beneficial to fighting the Japanese.
- The experienced troops will also be less rattled by air attack further diminishing that Japanese advantage.
The Japanese also had the benefit of momentum during the campaign, as they started winning they got more and more unstoppable because of the deficiencies mentioned. Reducing those deficiencies makes it far more likely that the Japanese can be stopped ,do that once and they have to build up which they cant afford to do if they want to keep advancing or risk taking very heavy casualties they can't afford if they want to keep advancing.
For Britain to win in Malaya they only need to do enough to blunt then stop the Japanese advance. Doing that is, while not easy, much easier than people seem to believe.
Good analysis.
In fact the difference in numbers was much less than believed - both sides had about 88,000, although the numerical advantage swung back and forwards as the campaign went on. I looked that up last night, damned if I can find it again.
As for the threat not being realised, it was, but the hot war in europe & north africa took precedence.
In 1937 the malaya garrison was 3 battalions of british, and 1 of indian troops.
By november 1940 it was 17 battalions, plus supporting artillery etc.
By december 1941 it was 47 battalions, plus supporting stuff, with more on the way.
Source (yes I know its wikipedia, but other sources don't disagree):
https://en.wikipedia.org/wiki/Malaya_Command#Allied_Land_Forces_(8_December_1941)
An increase of that magnitude, while there was strong demands for troops elsewhere, doesn't indicate to me that the threat was ignored.
With a lower level of crisis in the middle east, getting 1 experienced division with competent leaders, and a battalion of tanks, into Malaya from the off is probably enough.
The japanese had 3 divisions in the assault, and not enough transport capacity or available reserves to bring in very much more.
I had a look at the Japanese OOB for 1941/42 a year or so ago, and there was very little in reserve, anywhere.
My OOB file is in a format I can't attach, but I got it from here:
http://pwencycl.kgbudge.com/oob/jap_1.htm
In late 41/early 42 they were spread very thinly, with china as top priority, plus all the other invasions and stuff going on.
They were relying on swift and relatively low cost victories to free up troops, ships, aircraft and resources for use elsewhere.
Very hand-to-mouth, and run on either a tight budget, or a shoestring, depending on how you look at it.
And either military and logistical masterpiece, or a long string of successful gambles with the winnings reinvested, also depending on how you look at it.