Joshua was a captain during the Revolutionary War. He served in Colonel DuBois' regiment and was interned for a time at Dartmouth Prison.
From the New York Calendar of Wills, 1626 - 1836: 164 (B119) 1777, Septbr. 3 - 1778, May 27. Barnum, Joshua, of Dutchess Co. Wife Em, Sons Joshua, Azor, Eliahim [sic], Jonah, Noah, daughters Em and Hannah. Real and personal estate. Executors son Azor and Benejah Tubbs. Witnesses Joseph Crane, Nathl. Foster of Dutchess Co. yeoman, Allen Ball.