This letter was posted on June 13, 1775 from Joseph Warren to the Lieutenant Governor of Rhode Island. Warren was a physician who, after graduating from Harvard in 1759 and studying medicine, became interested in politics. He was a member of the Boston committee that prepared a report on the Boston Massacre in 1770. He was eventually appointed to Boston’s Committee of Correspondence, one of several such committees formed throughout the thirteen colonies. These committees became shadow governments, responsible for intercolonial communications, rallying citizens against British action, and uniting them for the first time politically. In Massachusetts, after the Battle of Lexington and Concord, the committees were superseded by the Massachusetts Provincial Congress, which controlled most of the countryside outside of Boston. While gaining an officer’s commission on June 14, Warren was eager for more direct military action than his rank (Major general) would normally allow. He volunteered as a private at Breed’s Hill and was killed by a musket ball to the head on June 17, 1775, only four days after this letter was written.
Warren sent his letter via the newly formed Massachusetts Provisional Post. The use of the term “Circular” indicates it was one of several sent to officials in other colonies. Prior to this, a Rhode Island printer named William Goddard had traveled through the colonies advocating the establishment of a postal system that would operate independently of the one controlled by the British. Several of the colonies took his advice and did so. On May 12, 1775, in Watertown, Massachusetts, the Provincial Congress established such a post, with the general post office at Cambridge. Other colonies followed suit, with Providence and Newport, Rhode Island doing so on May 30 and 31 respectively.
This letter indicated that Canadians were becoming concerned about military preparations being made in some of the Colonies, because of which they might join with the Six Nations (of the Iroquois), who were being stirred up by the British against the American patriots, and act on a hostile manner against the Americans. Specifically, Colonel Guy Johnson, a loyalist under orders from General Gage, recruited Iroquois warriors to join General Carleton in Canada for an attack on New England.