Freeciv

Right now combat happens in turns and ends "when one of the opponents is dead".

Instead, make it possible to have N rounds of combat. "N" will be defined in the ruleset, either globally, for a unit class or for each individual unit (preferably all of the above, with the more specific class overriding OR adding to the more general value).

Terrain can modify N, which is also defined in the ruleset (combat ends sooner in forest because it's easier to disengage or safely retreat).

For N=0 combat ends as before, "when one of the combatants dies".