This made the approach to the city from the south very difficult.
The brigade to which I was attached--Garland's, of Worth's division--was sent to confront San Antonio, two or three miles from St.Augustin Tlalpam, on the road to Churubusco and the City of Mexico.

The ground on which San Antonio stands is completely in the valley, and the surface of the land is only a little above the level of the lakes, and, except to the south-west, it was cut up by deep ditches filled with water.

To the south-west is the Pedregal--the volcanic rock before spoken of--over which cavalry or artillery could not be passed, and infantry would make but poor progress if confronted by an enemy.

From the position occupied by Garland's brigade, therefore, no movement could be made against the defences of San Antonio except to the front, and by a narrow causeway, over perfectly level ground, every inch of which was commanded by the enemy's artillery and infantry.

If Contreras, some three miles west and south, should fall into our hands, troops from there could move to the right flank of all the positions held by the enemy between us and the city.