Asa D. Chase was born in Carleton County, New Brunswick, in 1835. He may have married Mary Ann Sanburn of Woodstock, Carleton County, at Woodstock, on 26 September 1852, but this is unclear.

On 8 August 1862 Asa Chase enlisted in the Union Army to serve a term of three years during the American Civil War. He was discharged a private of Captain Witherell's Company D., 1st Regiment, Maine Veteran Infantry, on 1 June 1865, at Augusta, Maine. His discharge was issued by reason of a surgeon's certificate of disability arising from wounds received, on 12 May 1864, at the Battle of Spotsylvania (Virginia). The Battle of Spotsylvania Court House, which lasted for two weeks, was one of the most intense battles of the Civil War.

Chase's service in the Maine Veteran Infantry suggests that he served in other regiments during the Civil War. The 1st Regiment, Maine Veteran Infantry was organized 21 August 1864 at Charleston, Virginia, by consolidating veterans of the 5th, 6th, and 7th Regiments of Maine Volunteer Infantry. The 1st Regiment was attached to 3rd Brigade, 2nd Division, 6th Army Corps, Armies of the Shenandoah and Potomac to June 1865. Chase's discharge was stamped "Dickenson & Webster, Chicago, 29 February 1868," perhaps indicating that Chase may have moved west rather than returning to New Brunswick.