Arthur served in the New York militia during the Civil War. He began his service in 1858 as a brigade judge advocate, and rose to quartermaster general by the time he left near the end of 1862. As assistant quartermaster general, he supplied soldiers with food, proper uniforms, and equipment. Arthur saved the government money by contracting out services to the private sector. Governor Edwin Morgan, who had given Arthur his job and rank, praised him for his abilities: “He displayed not only great executive ability and unbending integrity, but great knowledge of Army regulations.”