Just for you Ren, a very brief return.
The "defile" is a valley, in my world a valley closed at one end. The Romans do not occupy the valley floor, instead they occupy the valley side slopes and ridge top (still the defile) inviting the opponents to occupy the base of the valley/defile. Obliging the enemy to climb the valley towards them both along the valley axis and up the valley sides, placing the Romans on the high ground, in these terms the "ridge tops".
The "defile" is a valley, in my world a valley closed at one end. The Romans do not occupy the valley floor, instead they occupy the valley side slopes and ridge top (still the defile) inviting the opponents to occupy the base of the valley/defile. Obliging the enemy to climb the valley towards them both along the valley axis and up the valley sides, placing the Romans on the high ground, in these terms the "ridge tops".
