Moylan's first battle, the
Battle of Wilson's Creek in Missouri, was fought on August 10, 1861. Moylan also participated in the
Battle of Fort Henry, Tennessee, on February 6, 1862, and in the
Battle of Fort Donelson, Tennessee, on February 11–16, 1862. Then the
Battle of Shiloh, Tennessee, April 6–7, 1862, and the
Siege of Corinth, Mississippi, from April 29 – May 30, 1862. On March 28, 1863, Moylan was promoted to the rank of second lieutenant in the
5th United States Cavalry. In this organization he fought in the
Battle of Gettysburg, Pennsylvania, July 1–3, 1863. On October 25, 1863, Lieutenant Moylan was dismissed from the service for being AWOL (absent without leave) in Washington, D.C. He then enlisted under the assumed name of Charles Thomas into the
4th Massachusetts Volunteer Cavalry Regiment on December 2, 1863. Moylan was appointed a sergeant in that regiment on December 26, 1863, a first lieutenant, then a captain on December 1, 1864. He was then brevetted to the rank of major on April 9, 1865, and mustered out in November 1865. After the war, he was elected as a companion of the California Commandery of the
Military Order of the Loyal Legion of the United States. ==Indian wars==