 In June 1865 Trenchard was appointed senior officer of the convoy service fleet, based at Cap-Haïtien, and was promoted to the rank of captain in July, then served as executive officer of the Brooklyn Navy Yard in 1866-69.On September 9, 1865, he fell overboard while attempting to assist a ferryboat which had collided with another vessel.One of his men, Seaman John Taylor, rescued him from the water, for which Taylor was later awarded the Medal of Honor.