The only drawback to horses was finding food and water for them. Troops were expected to move at walking speed so there was no need to have anything that would move any faster.

Horses were last used in combat by US forces during WW 1. The number one question asked when horses were expected to be used was would there be fodder for them on the other side of the enemy line? Once US forces broke through everyone would dismount in groups of four. Three men would guard the horses and one would see to it they were fed.

There were still horse mounted troops in the US military until the end of the Veit-Nam era, but they were mostly for show. There are only a few left now, and show is all they do.