Phelps gained intelligence by listening to British soldiers describe the defenses of the fort at a local farmhouse where he lodged for the night.  

He then went to the fort disguised as a peddler seeking a shave. He was able to collect information on the construction, strength and force of the garrison. While talking to the commander he remarked on one section that was in a dilapidated condition saying it would afford a feeble defense. The commander responded, “Yes, but that is not our greatest misfortune. All our powder is damaged, and before we can use it, we are obliged to dry and sift it.” Phelps reported his information to General Ethan Allen.He later helped finance and organize a militia which was assigned to General Washington’s army. He was present at the battles of Trenton and Princeton. In May 1779, Phelps was promoted to Colonel of the 18th Connecticut Regiment. After the war he was selected to be the Major General of the state militia.

His tombstone is engraved with “A Patriot of 1776. To such we are indebted for our Independence.”