The Commander is best used for Breaching due to the short time cycle between firing and the total firepower used, with enough firepower to knock down destructible walls in game with a single shot. Use this tactic to combat enemy Cornerdancing.
Snipers also have this ability, as do Grenadiers, however Commanders have the most success due to their rate of fire and by not using area effect weapons which may damage nearby units.
The best method for using this tactic is to set your squad movements to give you an attack advantage within the newly opened fire lane. It's a rare opponent who can predict where a wall may give in.
Breaching a door and entering into a new and unexplored room holds many uncertainties. Always assume there’s an enemy waiting on the other side and thus be prepared for any eventuality.
Always shoot doors and walls multiple times – just in case it doesn't work the first time when you send your orders in. If you do destroy the door/wall on the first shot, the excess shots will be ignored.
Using two units is advisable as one can provide backup once inside the room.
For the Commander the orders are as follows:
Attack door or wall two or three times (shift-right click on door) to verify doors destruction (random damage values may make first attack ineffective).
Press the <H> key twice to hold position for two seconds.
Force move into room - Ctrl-Left mouse click on intended breach and then Ctrl_Left click on the room beyond, ideally where there are light areas).
For the supporting unit (other troops) the orders are as follows:
Press the hold key a few times (<H>) or just use an Opportunity Fire command (in case an enemy pops out).
’Force move’ onto breached area. (Ctrl-Left mouse click on wall)
’Force move’ into room (Ctrl-Left mouse click on floor)
Alternatively, you can use the Commander to go through the breach, thereby reducing risk of shooting your own troops (and killing them) and then have the other troops use a Follow command, or just have them try to step where the Commander is, meaning they won't continue to move until the Commander moves.
AIs can use this tactic, particularly in crowded areas where breaking through a wall would allow Exterminators (XTs) to work through the breach. The only problem for an AI is its size - there are two sections of wall that must be taken out for the AI to move into the room, which means that during a ten second turn, the AI must knock it down to proceed.
Queens can chew through walls but face the same problems as the AI - size and movement through wall sections is extremely slow.