I expect they road into action with the troopers. I believe in the later US cavalry one or more farriers, sergeants or corporals, were assigned to each troop (80-100 troopers). Keep in mind these were not blacksmiths but troopers trained to care for the horses' feet with special tools and supplies carried with the rest of their saddle gear.

On route marches the horses needed constant attention and maintenance. At breaks in the march troopers were expected to first check on their mounts and calls were made up and down the line for the farriers. Allowing a horse to go unattended was cause for harsh discipline. All troopers carried spare shoes and nails in their saddle bags and were expected to assist the farriers and make minor "repairs" as their skill and experience allowed.

Russ