Hello there
I recently had very good experiences as a world conquest UK on very hard. It was a custom game, but div building should still apply.
If you plan to let Ger take out France, lots of Mot and Arm are not required. If you do want to save France, fast Arm would be better.
I abandoned everyone to reconquer them later with specialized light forces where and when they very needed.
My workhorses were "Light Infantry Corps" without many support brigades and "Light Armored Corps" with 3 LArm Divisions and 2 Arm Divisions as backup.
The reasoning is that you will be fighting a lot in bad terrain and bad Infrastructure against weaker and exposed enemies, so you only need a couple of heavy Divisions here and there. If you find yourself lacking in firepower, you might be overstretched. Hold the line in one theatre with minimal specialized Divisions and ship in reinforcments to a Front you can finish fast, then use those freed forces to strike back somewhere else.
UK lacks Manpower to hold every Front simultaneously with "general purpose" Divisions. Arm would be the obvious choice to conserve MP, but drains supply, underperforms in bad terrain, and results in you having less total Divisions, which is bad if you want to attack the SU.
So I went with mostly 4xInf, LArm and Special Forces for offense that get switched out with 3xInf with Support Brigades and Arm for defense on favourable chokepoints.
My Corps Setups: (All HQs were reinforced with 2xInf+Art and (+At) with Superior Firepower)
"Light Inf Corps"
3 Div of 4xInf
1 Div of 3xInf+Art
1 Div of 3xInf+At
The last Division with At was unnecessary, as kovax explained, I kept it in case I needed those Corps later against Ger, US and Sov, or against surprise Armor, but by this time I had enough "Heavy Inf Corps" with more AT.
Any other Brigade would have been more useful, another Art or Inf or AC or Eng, or even just 3xInf to be honest.
I had 3 such Corps ready for the war and one more to build. Then I focused on "Heavy Inf Corps"
4xInf can easily deal with anything except Arm and in any Terrain. The downside is the high use of Manpower. Air Power is absolutely needed to keep casualties low and 4×Inf should never be wasted to starve or freeze in hostile occupied terrain.
To Hold the Line, I instead used "Heavy Inf Corps":
2 Div of 3xInf+Art
1 Div of 3xInf+At
1 Div of 4xInf
1 Div of 2xInf+Art+At(+Inf with SF)
This is a more defensive build that holds what the Light Inf conquered, and later as Line Infantry against Ger and Sov.
Might even go with 2xInf+2xArt to further save manpower and frontage.
The single 4xInf is nice for counter offensives with river crossings or mountains.
I had two ready for war and kept building those, as my need to Hold the Line increased with each new theatre my light troops engaged in.
I had 2 "Light Arm Corps" that did most of the actual fighting and not only exploitation all over the world where mobility was key.
2 Div of LArm+Mot+AC
1 Div of LArm+Mot+Eng
1 Div of Arm+Mot+TD+Eng
1 Div of Arm+Mot+TD+Ac
The LArm is strong enough to tip the balance in a hard battle by joining from the flank.
The Arm is used whenever my Light forces were not enough and in case enemy Arm shows up.
I found the Eng really, really helped with its mobility bonus to cross bad terrain and rivers, even though this Div is slower on plains and weak in a straight fight, but that was not its purpose. You fight to win quicker, not to win in a fair fight. For this, you sometimes need to be fast even when going through mountains.
I thought about adding SpArt later, but that would have been bad in the Terrain those Corps were fighting in. I swapped the Mot for Mech for fighting the SU though.
I had two more Corps of 4 Div with Arm and 1 Div Larm ready when I wanted to take on Germany with one more corps ready for the USA.
This was supplemented with 1 Corps of Marines (3 Div 4xMar, 1 Div 3xMar+Arm(+Mar), 1 Div 2xInf+Art+At(+Inf)),
1 Corps of Mountaineers (4 Div 4xMtn, 1 Div 2xInf+Art+At(+Inf)),
and one Corps of general purpose Special Forces (1 Div 4xMar, 1 Div 4xMtn, 2 Div 4x Par, 1 Div 2xInf+Art+At(+Inf),
Later i built another one more of each Corps.
As you can see, my Corps were standardized to be shipped around where they were needed, with different Divs that do one thing well. Each Corps had at least some capacity to hold a Province well, deal with Arm or attack in bad Terrain.
4xInf seem to be quite underappreciated in the Forum. Their downsides are:
- High MP usage (definitely bad for UK, they must be supplemented with planes and specialists),
- high frontage (not an issue if used correctly),
- high officer usage (UK can deal with that),
- do not excel in anything (again, supplement with specialists when and where needed),
- too expensive to use as just a "filler" division that closes a gap in the Front without fighting,
- slow in plains,
- not perfectly efficient in the big end game war vs. the SU
- boring
But I think the upsides count more for UK specifically:
- beats any non-Arm-Division that the AI uses 1 on 1.
- holds provinces very well until specialized reinforcments arrive if outnumbered
- holds long enough for your air forces to make an impact
- contributes in any terrain except forts, gives you the ability to attack in any direction
- can perform lightly contested landings
- faster then Inf+Support in bad terrain
- cheaper and faster to build then Mar and Mtn for regions where you don't want to commit those.
To be honest, you probably don't need to be that elaborate and could just spam 3×Inf divisions and build a few Corps of Arm, Larm and Mar with a similiar strategy: Use the specialists to win hard fights, swap them out with Inf to hold the line in favourable defensive positions, and use your specialists to win a different theatre, then come back with your freed up troops.
That means, more important then division building is to choose your battles cleverly. Use whatever troops are good enough in one theatre to slightly outgun your enemy, gain lots of experience in battle and use your freed up, battle hardened troops to gain the advantage in progressively harder battles in a different theatre
Hope that helps!