Eugene Marshall was born in North Bridgewater (Mass.) on July 10, 1832. He later moved west to Sheboygan, Wisconsin (1852), and to Caledonia, Minnesota, where he served (1853-1861) as Houston County Surveyor. He enlisted in the third company of Minnesota volunteer cavalry and saw service with them in Tennessee (1861-1862) as part of the Fifth Iowa Cavalry. He continued service with his company when it re-enlisted as Company C of Brackett's Battalion in the 1864-1865 punitive expeditions against Dakota Indians in Minnesota and in Dakota Territory. Following the war, he returned to Caledonia, where he married Elizabeth Willard in 1866. They moved to Hancock, Iowa in 1868, but returned to Caledonia in 1880 from which time Marshall served as cashier of the Caledonia Bank.

Companies 1-3 of Minnesota Light Cavalry enlisted at Fort Snelling during September-December 1861. The third company was commanded by Captain Alfred B. Brackett. They were joined in November by a fourth cavalry company commanded by Captain Von Minden. In December they were assigned to a larger cavalry unit known as the Curtis Horse Regiment. The regiment saw light action in Tennessee throughout 1862 and 1863. They participated in the Battle of Fort Donelson (Feb.), in the Battle of Pittsburgh Landing (April), in the Siege of Corinth, and in the Clarksville Fight, as well as a number of smaller actions. In the summer of 1862 they were placed in the Fifth Iowa Cavalry regiment. This caused a good deal of unrest among the three Minnesota companies, which felt that they had lost much of their home state identity.

Therefore, when their original enlistment had been served, the Minnesota companies re-enlisted (Jan. 1864) and were detached as Brackett's Battalion of Minnesota Volunteer Cavalry. The battalion was thereupon reassigned to the Dakota Indian campaign then being prosecuted in Minnesota and in Dakota Territory. They served in that duty from March 1864 through 1865, following which they were disbanded at Fort Snelling.