the regiment's first important service was in the maryland campaign of 1862. at the battle of antietam, one of its squadrons was involved in the first attacks of the day. at the battle of fredericksburg, devin inherited command of david mcmurtrie gregg's cavalry brigade, when the latter took charge of the brigade of george dashiell bayard, who had been killed by confederate artillery fire. at the battle of chancellorsville in 1863, his small brigade was the only cavalry not detached for brig. gen. george stoneman's raid and he successfully led three union corps on the stealthy flanking march that preceded the battle. the men of the brigade repeatedly distinguished themselves in the heavy fighting of the battle. they suffered almost 200 casualties in the battle, higher losses than union cavalry units had seen prior to that time. devin also led his brigade in the battle of brandy station (june 9, 1863), and took command of brig. gen. john buford's division while buford commanded the entire right wing of the two-pronged attack on confederate cavalry. while observing the skirmish line early in the fighting, devin had his horse shot out from under him.