He is best known as the commander of the Artillery Reserve of the Army of the Potomac, including at the Battle of Gettysburg in July 1863, where many of his batteries played important role in the Union victory.
Han er bedst kendt som leder af artillerireserven i Army of the Potomac, bl.a. i Slaget ved Gettysburg i juli 1863, hvor mange af hans artilleribatterier spillede en stor rolle i Unionens sejr.