EX: If a +50% against Melee Units has a +20% City Attack upgrade, and it attacks a city which is defended by a melee unit, does it get both bonuses?

Matt

Yes.

They also keep the upgrade after you upgrade it to another troop type.

But how do they stack? Do they stack arithmetically (i.e., do +50% and +20% give you +70%)? Or do they stack geometrically (i.e., do +50% and +20% give you 150%x120% = 180% = +80%)?

They stack on the base strength modifier I believe.

The game adds the percentages together then multiplies the strength by the percent, I believe.

For example, an Axeman with Combat 2 would be strength 8.5 vs a melee unit.