On 9/9/1775, Ambrose Ramsey was commissioned as Colonel/Commandant over the Chatham County Regiment of Militia, a position he held until the end of the war.

On February 1, 1781, Brig. Gen. (Pro Tempore) William Lee Davidson, of the Salisbury District Brigade of Militia, was killed in action at the battle of Cowan's Ford. Earlier, Brig. Gen. Griffith Rutherford had been captured at the battle of Camden, SC on 8/16/1780, and he was still in confinement. In February of 1781, the Colonels of the Salisbury District convinced the newly-commissioned Brig. Gen. Andrew Pickens of South Carolina to temporarily lead their brigade since he had no men assigned to him as yet in South Carolina, and since he was currently following Brig. Gen. Daniel Morgan and Maj. Gen. Nathanael Greene in their "Race to the Dan" with Lt. Gen. Charles, Lord Cornwallis. In early March of 1781, Brig. Gen. Andrew Pickens needed to return to South Carolina.

As the large Patriot force was gathering around Guilford Court House for the fateful battle with the British (on 3/15/1781), Col. Ambrose Ramsey was temporarily appointed to lead the Salisbury District Brigade of Militia, possibly just for the day of the battle, but perhaps for a short duration longer - records are unclear. It is clear that he was soon back to his regular duties as Colonel/Commandant over the Chatham County Regiment of Militia.

On 7/17/1781, Loyalist militia leader, Col. David Fanning, captured Col. Ambrose Ramsey and fifty-three other Patriots at Chatham Court House. Col. Fanning paroled all of the Patriots except for fourteen men, including Col. Ambrose Ramsey. These fourteen were taken to Wilmington and turned over to Maj. James H. Craig, the British commander in the occupied Wilmington at that point in time. It is unclear just how long Col. Ambrose Ramsey was detained, but it is thought that he was released - on parole - when Maj. Craig evacuated Wilmington on 11/18/1781.

After the war, Ambrose Ramsey was commissioned as Brigadier General over the Hillsborough District Brigade of Militia on November 23, 1784, soon after John Butler resigned. Brig. Gen. Ambrose Ramsey resigned on December 7, 1789, and he was replaced by Alexander Mebane.