Civ 3 generalizes combat so you dont have to worry about the nitty-gritty details, it is a strategic game not a tactical ones.
Try out Age of Empires style of games, they have the type of combat you describe. Imagine the micromanagement nightmares and complex combat systems needed for this in a Civ game.
Personally I think armies are kinda silly, id rather just have them to rush wonders or maybe give a 'morale' bonus to units stacked on the same square.
Although it is entertaining to watch Napolean throw his arm yelling HO! as modern tanks decimate their enemies