however, you can now set up a fort i na tactical position that allows no army to get past you. then if they try to counter-attack, they will either have to attack a well-defended position, or be attacked from a preferrably uphill position.

also, now if you incur losses you can easily retrain them in the surrendered city. remember: unlike previous games, any unit can be re-trained in any city with a working barracks/ town center.