Originally from Larchmont, New York, Rear Admiral Lennon graduated with distinction from the U.S. Naval Academy with a degree in mathematics. Following nuclear power training, he served in the engineering department of USS Daniel Webster (SSBN 626) during its final two patrols and participated in its nuclear refuelling overhaul.
While assigned to submarine reserve detachments, he gained experience in force protection, guided missile submarine operations, and diesel boats. As a member of Submarine Advisory Teams, he served at sea aboard carriers and a destroyer coordinating submarine operations with naval battle groups.
Lennon directed operations during a joint military exercise in Ukraine while serving with the Sixth Fleet, and he led civil military discussions in Estonia supporting research into countering hybrid threats while assigned to NATO Allied Command for Transformation.
In support of Naval Forces Africa, he supervised the historic first visit of an Algerian naval ship to America. Later in Algiers, he continued to develop the working relationship between the U.S. and Algerian militaries. Additionally he was Director of a multinational exercise in Senegal where he oversaw the training of African naval forces in counter trafficking and counter illegal fishing operations.
As Reserve Deputy Commander, Submarine Forces, he developed relationships with South American navies and supported U.S. strategic nuclear deterrence as an Airborne Emergency Action Officer. The 1,600 Sailors he led in Submarine Force Reserve Component conducted undersea warfare operations and submarine maintenance.
Lennon has commanded five reserve detachments and has earned master's degrees from Johns Hopkins University and The George Washington University.
As Commander, Submarines NATO, Lennon is responsible for multinational submarine safety and operational tasking of submarines assigned to the alliance.