Pelham was involved in every major military engagement of Stuart's cavalry from the First Battle of Bull Run to Kelly's Ford, more than 60 encounters. He is noted as the Chief of Stuart's Artillery in the Battle of Antietam (Sharpsburg) and Battle of Fredericksburg. At Sharpsburg, Pelham's guns, positioned on a rise known as Nicodemus Hill, repeatedly harassed the flanks of oncoming Union lines, causing numerous casualties and breaking up battle formations.