Kreigspiel it is!
The HMG that stopped firing on you was the one streaming down from a bunker at the top of the wall - which, the LT does not know, has just been bushwacked by part of your Platoon!
The Dimension Door scrolls are a go-er if you wanted to port up to the enemy position and engage quickly - but remember, that spell's great limitation is that you can take yourself and one additional person.