Denning was a sergeant in the Continental Army from March 1778 until April 1780. He was stationed near Carlisle at Washingtonburg Forge, now the Carlisle Barracks. While stationed there, Denning explored and mastered the technique of creating lighter and easier to transport cannons. He did this by welding strips of wrought iron together in layers and building the cannon with the layers. Denning lived out his life following the Revolution near Newville. His grave can be found in the cemetery of Big Spring Presbyterian Church in Newville.