Freed in 1774 when his indenture expired, Haynes joined the minutemen of Granville. In 1775, he marched with his militia company to Roxbury, Massachusetts, following the news of the Battles of Lexington and Concord. In 1776, he accompanied them in the garrisoning of the recently captured Fort Ticonderoga. He remained on garrison duty until contracting Typhus, which caused him to return home.