Rotating troops at the front of battle

[LorDBulA]

I do it very rarely but when I do it I use this approach:

The way I do it is bring up the replacement and have them engage the target of the unit they're replacing. Once they've started to push forward into the enemy, I'll withdraw the first unit and send them to the rear. Doing it this way minimizes casualties effectively.

Just make sure that you use Alt button for retreating units so they dont wheel around before marching off.