For a few months in 1776, he was chaplain to the 11th Massachusetts Regiment commanded by Colonel Ebenezer Francis, raised for the defense of Boston. In 1778, he became chaplain to General Jonathan Titcomb's brigade and took part in General John Sullivan's expedition to Rhode Island. Soon after his return from this expedition he trained in medicine to supplement the scanty income of a minister. In 1782, he established a private boarding school, directing it for nearly a quarter of a century.