The Massachusetts militia began the American Revolutionary War at the Battles of Lexington and Concord,[37] The Massachusetts militia units were mobilized either during or shortly after the above battles and used to form, along with units from Rhode Island, Connecticut and New Hampshire, the Army of Observation during the Siege of Boston. On July 3, 1775 General George Washington, under the authority of the Continental Congress, assumed command of the Army of Observation and the new organization became the Continental Army from which the United States Army traces its origins.[citation needed]