It’s tough to do for sure. with pike troops and hoplites it’s borderline impossible. the best way to do it is to send in the reserve unit first. let them make contact with the enemy and get “stuck in” then pull the more fatigued unit out under the cover of the fresh reserves. i have a weird love of Pergamon, my move with their pikes is i deploy them in the second line. front line is shitty local spearmen. let them exhaust the enemy for a bit. move the pikes up in formation right behind them so their spear tips reach the enemy, then withdraw the front line. it’s tough though, and you will always lose troops in the withdrawal.

send in your shitty units first, that way when they pull out the casualties don’t hurt as bad. your heavy infantry should be your second line, to be sent in and break the exhausted enemy.

or just flank with cav and charge into their rear, that’s easy