Col Herbert J. Slocum, U.S. 13th Cavalry. Slocum was in command of the 13th Cavalry Regiment at Columbus New Mexico, or more accurately Camp Furlong which was next to Columbus.
They expected to encounter an American garrison of only 30 men, as noted above, based upon their scouting and intelligence. However, Columbus had a garrison of over 300 men, to Villa's force of approximately 500 men. The US forces were from the U.S. 13th Cavalry who occupied adjacent Camp Furlong. Moreover, U.S. troops were equipped in a modern fashion, complete with the Benet Mercie light machine gun which had been adopted for cavalry use.