I just picked up the Heroes of Might and Magic series and started playing HOMM1. Here is a question that comes to mind:

How many Peasants does a Level 1 Knight Hero with no spells need to defeat 5 stacks of 10 Ghosts?

The number I get is 42250. It is based on the assumption that the ghosts are hitting for 6x1.5=9 damage and the stacks will grow to 100, then 1000. Casualties will be 2250. The stack of 40000 Peasants will then take out the stack of 1000 Ghosts.

I like your math.

Peasants are great units, but not for attacking. They can absorb turns from enemies that allow your more costly ranged units time to do enough damage to kill off any threats before others can get to them.

I loved HOMM1. I'm glad someone's playing it. Enjoy!

You should need significantly less if the peasants are split into multiple stacks so that you can eliminate all the ghosts in the first round (before the resulting stacks of 100 ghosts have a chance to bolster their numbers further). 100 ghosts have 2000 HP to burn through, so I'd estimate around 4000 peasants to one-shot such a stack (once attack and defense are taken into account, assuming the hero isn't contributing much there); the peasants lost during the first round are mostly a rounding error in all this. So four stacks of 4000 peasants should be able to take out five stacks of 10->100 ghosts in the first turn (at least one counterattack plus four regular attacks, fewer stacks required if the ghosts go after more than one peasant stack during the turn, bringing on additional counterattacks). Tactics also have the potential to tweak these numbers a bit; if the ghosts cluster in such a way that a stack of peasants can't reach them in the first turn then the number of peasants is woefully insufficient (and your numbers are required). On the other hand, depending on the AI the ghosts use to choose their targets it may be possible guarantee two or more counterattacks during the round, thus reducing the peasants required to 3 stacks of 4000. So unless I'm missing something in my analysis you'd only need 16,000 peasants maximum, and possibly be able to manage it with 12,000.

Did Heroes 1 allow you to split stacks? I thought that was possible only on newer installments of the game.

I think JMich is right, but I won't test it (my HOMM1 are 600 miles away in my mother's attic). But I am enjoying people spending their limited time on this earth solving this ridiculous question. And this is why I love GOG.

I'm almost certain you can't split stack in HoMM1 (the only game of the series), but I finished the game ages ago so maybe I'm wrong...

There are only a few early-game uses I can think of for the peasants. They seem to be available in large enough quantities early in the game to do something like take out small stacks. It is a very short window of opportunity where they are useful.

Wasting a turn seems to be another use. It might be funny to just buy one for 20 gold and watch something big waste an entire turn eating that one Peasant. I just started to play it. I am playing the Ironfist campaign and am two and a half weeks into Scenario 2. I have the game saved at the start of the second month. The main hero has captured the town and crystal mine in the southwest corner of the island. The goal for this week is to hire another (Barbarian) hero whose main purpose will be to run fresh troops to the main hero. The main hero will capture the third city and gold mine. This will provide the economic base for taking over and making good use of the Warlock island to the northwest.

Do you remember how long it is supposed to take to win this scenario? Sometimes ridiculous questions lead to more serious discussions. :) The idea of Ghosts killing peasants and growing to ridiculous stacks while the other stacks are not big enough to kill the Ghost stacks which keep getting bigger made me think of the original question.

Then there is the Turn Undead spell which eliminates the entire stack. Who ya gonna call?

Yes, stack splitting would be useful, but if it can be done in HOMM1, then I do not know how to do it.

I don't remember stack-splitting, but I'm pretty sure you can't do it.

I'm gonna call Ghost Busters!

And I don't now how long the scenario is, but none were terribly long. I usually had a max of a few hour per scenario until towards the end. I remember those being especially big -- but till nothing like a few of the maps in HOMM3 that took many days of playing to finally conquer.

Guess that's what I get for only playing a very cursory amount of HoMM1. In light of not being able to split stacks it looks like the OPs numbers are the correct ones.

1 Ghost vs 1 Peasant damage calculation: (100% + (8 - 1) * 10%) * {4; 6} = 6,8-10,2. 8,5 on average.

So, on average, stack of 10 Ghosts will grow to 95, killing 85 peasants. As they go first, there will be at least 255 casualties if peasants are in corner after first turn. Peasants retaliate, 4 packs left. Peasants strike, 3 packs left.

Next time they will grow to 902,5 (on average), killing 807.5 peasants. 2422,5 casualties. 1 pack left after retaliate and peasants strike.

Next turn, ghosts: 8573,75, killing 7671,25 peasants and then they die on retaliation.
Max. Ghosts in stack: 8573,75.
Peasants have damage penalty of 60% against Ghosts.
Therefore total Peasants needed: (14 290 * 20) + 2422,5 + 255 = 288 478 (rounded up)..

Correct me if I am wrong somewhere (I might be wrong about retaliation part).
Also Knight gives passive Attack/Defense bonuses, depending on hero, so it will make some numbers differ by 10%-20%.
HoMM1 won't allow you to have so many peasants in 1 stack. So it will be impossible task.

Edit: apparently I calculated it wrong and forgot Ghosts' HP, which is 20.

HoMM1 doesn't allow to split same stack in multiple mini-stacks IIRC (it was feature of later Heroes). It won't allow to have over 32767 units in one stack either.