During the Revolutionary War, Richard was a captain in Brigadier General Gold Selleck Silliman's 4th Brigade, Colonel Nehemiah Bardsley's 16th Regiment of Connecticut Militia. Colonel Bardsley was in command of the 16th Regiment from February 1778 to the end of the war in 1783; the exact dates of Richard's captaincy are not known.
From Connecticut Historical Society. (2015). Rolls and lists of Connecticut men in the Revolution, 1775-1783 (original spelling and punctuation): Capt. Barnum's Company. A Pay Abstract for Horse travel Belonging to the 4 Alarm List Company in Danbury in the 16 Redgment of Militia in the State of Connecticut Commanded By Nehemiah Bardsley Col. In a Late Expidition to Farfield Norwalk &c for the Defence of this State and the Rest of the United States of Amaricah, July the 7 1779
Officers and Soldiers names That Rode on Horse Back
Richard Barnum Cap.
Nathaniel Barnum Lieut. [possibly Richard's son Isaac Nathaniel Barnum (1780-1869)]
[also included were the names of three sergeants, a clerk, two corporals, a drummer and 21 privates]
His will was probated in 1783.