He enlisted as a lieutenant of a company of
Minutemen in April 1775. Oliver was promoted to captain in the
3rd Massachusetts Regiment in 1776, major in the
2nd Massachusetts in November 1777 or 3rd Massachusetts (November 1, 1777–January 1, 1783) and lieutenant colonel in the militia in 1779. For example, Major Oliver and other officers of the
Massachusetts Line signed a June 13, 1779, letter to George Washington regarding issues they had with how promotions were being handled. Oliver is an
original member of the Society of the Cincinnati. ==Post-war==