American Military History, Volume 1

On the morning of February 21 scouts brought word to General Taylor that a great Mexican army was advancing, preceded by a large body of cavalry swinging east to block the road between Agua Nueva and Saltillo. That afternoon Taylor withdrew his forces up the Saltillo road about 15 miles to a better defensive position near the hacienda Buena Vista, a few miles south of Saltillo. There, a mile south of the clay-roofed ranch buildings, mountain spurs came down to the road on the east, the longest and highest known as La Angostura; between them was a wide plateau cut by two deep ravines. West of the road was a network of gullies backed by a line of high hills. Leaving General Wool to deploy the troops, Taylor rode off to Saltillo to look after his defenses there.

By next morning, Washington's Birthday (the password was "Honor to Washington"), the little American army of fewer than 5,000 troops, most of them green volunteers, was in position to meet a Mexican army more than three times its size. The American main body was east of the road near La Angostura, where artillery had been emplaced, commanding the road. West of the road, the gullies were thought to be sufficient protection.