The only army Santa Anna had to protect his capital and the mountain passes west of Vera Cruz, was the one he had with him confronting General Taylor.

It is not likely that he would have gone as far north as Monterey to attack the United States troops when he knew his country was threatened with invasion further south.

When Taylor moved to Saltillo and then advanced on to Buena Vista, Santa Anna crossed the desert confronting the invading army, hoping no doubt to crush it and get back in time to meet General Scott in the mountain passes west of Vera Cruz.

His attack on Taylor was disastrous to the Mexican army, but, notwithstanding this, he marched his army to Cerro Gordo, a distance not much short of one thousand miles by the line he had to travel, in time to intrench himself well before Scott got there.

If he had been successful at Buena Vista his troops would no doubt have made a more stubborn resistance at Cerro Gordo.