> Trebuchets cause collateral damage, and so do knights. Individual trebuchets will lose to musketmen but as a group they will cause enough collateral damage to allow a stack of other units to finish them off.

But Trebuchets only have 1 movement. You're not attacking a group of Musketeers in the open field unless your opponent is letting you do so.

So now the question is: how do you get your Trebs close enough to the opponent's death stack such that you can effectively attack them with collateral damage? Hint: it involves a death stack of your own Musketeers.

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Lets game this out really quick. Lets have a simple field with 3 locations:

* T . M

Where "T" is the Treb-stack, and "M" is the Musketeer stack. Both units have 1 movement. Lets game what happens if the Trebs approach.

* . T M

Okay, that's the Treb's turn: 1-movement per turn. The Musketeers now murder the entire stack of Trebs, because 9-attack Musketers wreak 4-attack Trebs. All the Trebs die, the Musketeers spend maybe 2 or 3 turns healing up from combat. Musketeers don't even need collateral damage, they just kill the Trebs in straight combat.

You might think things are symmetrical, but they're really not. The Musketeer stack does NOT have to stay as a stack. If the Trebs defend, the Musketeer turn happens as follows:

* T m M

Where "m" is just 1-Musketeer. Now what do the Trebs do? If you attack the "m" singular Musketeer, your Treb almost certainly dies without inflicting collateral damage (4 vs 9 strength is basically a guaranteed win for the Musketeer. Even with a 20% Retreat upgrade, we're looking at a near 80% chance of losing your Treb).

You can attack the lone musketeer with multiple units (1st Treb dies, but maybe the 2nd or 3rd Treb wins). If you dedicate a 2nd or 3rd treb to the combat, you're left with the following situation:

* T t M

After the 2nd or 3rd Treb wins combat, they enter the tile, damaged from combat.

And now its the Musketeer turn. They kill the Treb (9 vs 4 again, taking very little damage), and we're back to...

* T m M

A match that your Treb stack is almost certainly losing.

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The answer: The Trebs retreat to the nearest city, and hope that the Musketeers are stupid enough to chase. At a higher tactical level, the Musketeer owner will not be so dumb, but will instead invoke map control at this point. (Pillage and deny resources, find soft targets, etc. etc.). Attacking cities is very hard in all Civ games, so map-control is usually what you're aiming for.

Answer #2: Have a death-stack of your own Musketeers, allowing your Trebs to approach the opponent stack. This only really works if you have more Musketeers than your opponent. Thereby: leading to the "Death-stack" game where both sides simply build bigger and bigger balls of Musketeers in order to do anything relevant in combat.

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> knights

It has been a long time since I played Civ4, but I don't recall knights having collateral damage. I've checked the game manual (https://steamcdn-a.akamaihd.net/steam/apps/3900/manuals/manu...) as well as the Civ4 Wiki, no mention of collateral damage.

What Knights have are Flank attacks (https://civilization.fandom.com/wiki/Flank_attack_(Civ4)), which allow them to wipe out Treb-stacks with ease. But this does NOT apply to Musketeers.