Towards the end of the HT spam thread there was a discussion on which unit would best complement a heavy tank. I put some thoughts down early in that thread, when I was determining my stack composition strategy, and wanted to revisit and run some numbers.

In these situations, I've assumed no doctrine, no terrain boosts, and the following levels:
- Heavy Tank L2, avail. day 10
- Infantry L4, day 8
- Anti Air L4, day 10
- Mot Inf L3, day 8
- Mech Inf L2, day 8
so that all are available at comparable times.

tl;dr answer: Infantry are a mediocre pairing with HTs assuming stack sizes remain under 10. Once stack size goes above 10, the value of specialists increases even further. If not AA, the best unit to pair with HTs is probably Mech Inf.

Analysis: Comparing five stacks:
- Stack 1: 5 HTs (baseline)
- Stack 2: 5 HTs, 5 Inf
- Stack 3: 5 HTs, 5 AA
- Stack 4: 5 HTs, 4 Mot Inf
- Stack 5: 5 HTs, 4 Mech Inf
(Dropped a unit from 4 and 5 to keep MP close)

Costs:

Performance against the various dimensions that matter for land units:

Infantry (S2) seem... OK?
- Infantry only excel in defense against other UA units. This is nice to have if we expect to be on the defensive, but usually expanding players are the ones attacking. The Mech Inf stack (S5) is only 8% behind, too.
- Infantry have decent anti-air defense, but obviously trail the true AA stack (S3), 90 to 38. S2 only barely exceeds S5 again, this time by about 10%, 38 to 34. Importantly, neither is enough to deter planes.
- Infantry add some attack against UA, but still trail S4 and S5 by about 13%. This is likely a more common situation than defense, so extra attack is more important than extra defense.

Note, Mech Inf (S5) is strictly stronger than Mot Inf (S4) across all dimensions, despite costing barely more as a stack: <3% more in resources and <1% more in MP. Offensively they're comparable, but defensively the Mech Inf produce a stack with 10% more defense against HA and 26% (!) more defense against UA.

One way to quantitatively compare the efficiency of each of the stacks is to sum total damage for all dimensions and divide by resources or manpower:

Infantry does OK, slightly in the lead in efficiency of total resources (though not MP).

So if we could only choose a single unit, which one pairs best with HTs in small stacks? I'd still choose AA, valuing the true deterrence vs planes, lower manpower cost, and extra HP above the added damage against unarmored. If somehow I knew no one will use planes, I think the effectiveness ranking looks something like Mech Inf >> Mot Inf > Inf. Infantry have a more complementary resource requirement to heavy tanks, though, so if Metal or Oil costs are a constraint then I think Infantry makes an OK choice.

... but that's limiting ourselves to 10 units. There are plenty of reasons to overstack, which I'll skip, and jump to assuming that we want 10 HTs in each stack. In this case, which unit pairs best?

- Stack 1: 10 HTs (baseline)
- Stack 2: 10 HTs, 10 Inf
- Stack 3: 10 HTs, 10 AA
- Stack 4: 10 HTs, 8 Mot Inf
- Stack 5: 10 HTs, 8 Mech Inf
(Dropped two units from 4 and 5 to keep MP close)



Compared to our baseline:
- S2 only contributes def against UA (+50%) and def against planes (+50%, but at 45 damage it's still not enough to deter attack)
- S3 (AA) has five times the defense against planes (3.3 x S2), and no longer trails S2 in attack against UA
- S4 and S5 add 50% to attack against UA, but no longer provide attack against armor. S5 (our Mech Inf stack) is now strictly stronger than S2 and S4 in all dimensions and actually costs less manpower than S2.

Quantitatively, looking at damage per resources and manpower:

It's easy to see how the 10-unit maximum comes into play. Many lines overlap because the supporting units don't do things better than the HTs. I think this makes the case for AA even stronger--it turns a weakness into a strength while being more efficient than other units in both manpower and resources. If not AA, then Mech Inf seems like the next best choice. Given the unlikeliness of defending, and the fact that it won't deter planes, I actually think the Infantry stack is worse than a stack of 10 unsupported HTs. For the MP spent adding 10 Inf, you could produce almost seven more heavy tanks--and those clearly do just fine by themselves as shown by the stats above.

A different comparison showing the strength of AA: Stack 2 (10 HT / 10 Inf) vs a stack of 10 HT and just 2 AA, now called Stack 1:


Other than defense against UA this stack performs as good as our 10 Inf stack while costing 2/3 of the MP.

If not limited, should we add anything other than AA? Here's a comparison between 10 HT vs 10 HT / 10 AA vs 10 HT / 10 AA / 10 Mech Inf.

40% more resources and 50% more MP gets you:

More Atk and Def against UA. Total efficiency isn't great, though:

I'd say that going beyond AA isn't necessary.
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(Disclaimer: many other considerations for stack composition: speed, doctrine boosts, terrain boosts, enemy unit types, resource limitations, time/factory constraints... a long list)

It's an interesting question, tough to answer. My guess is that Urban is the most common terrain for melee battles and so it might be worth strengthening our stack in Urban terrain. More generally, it seems like faster stacks or doctrines can choose their battle location better than slow stacks or doctrines, so faster stacks may be able to go all-out on particular terrains while slow stacks may want to smooth over weaknesses and be more balanced across all terrains.

Running the numbers with some changing terrains, I don't think it changes our results much. Seems like AA is the only option for deterring planes, and Mech Inf is probably the best pairing for ground attack. Inf looks OK though.

Here's our 5 HT + X stack comparison, repeated from above (1: HT, 2: Inf, 3: AA, 4: Mot Inf, 5: Mech Inf)

And here's what it looks like in Urban:

It's certainly much better, but it's still not enough anti-air to be a true deterrence and the attacking strength still trails Mech Inf and Mot Inf (which get small Urban boosts as well).

Bumping up to our overstacked scenario where it's 10 HT + X (same as above):

And now in Urban terrain:

Inf looks much better again, and now differentiates itself in attack vs UA from the base 10 HT stack, but it still trails Mech and Mot Inf. I think the choice is still AA vs Mech Inf.

Commandos look appealing in Forest and Mountains, but they provide basically no benefit in other terrains. Still not worth the investment imo. Here's a comparison in Mountain terrain for:
1: 10 HTs
2: 10 HTs + 10 Inf
3: 10 HTs + 8 Commandos
4: 10 HTs + 8 Mech Inf


As to the RRG comment, if we're going to build any RRGs we should probably go all out on them. This is all a fun hypothetical where we limit ourselves to melee units. I wouldn't want to actually produce heavy tanks if it meant taking resources away from RRGs.

Yea it'd be interesting to look at this across all stacks, not just per stack, and add in a calculation of manpower and resources saved by upgrading starting infantry rather than producing all from scratch. This benefit will dilute as we make more and more stacks but we could probably make some assumptions and figure it out.

Militia fill that role better imo

Welp this analysis might already be useless after today's balancing changes haha