back to my original question

1 stand up on the wall as can fit in between 2 defenders, 2 stands down below waiting to climb the ladders. opponents turn, the 2 flanking lines of infantry that didn't cover the wall entirely uses initiative to attack both sides of the men that snuck on. The 1 stand loses but with no casualties, do they go back down their ladder? Or do they go left or right, their choice and in doing so, lose the stand on the wall as a retreat would bring it into contact with an enemy stand?