He is most noted for his service as a company commander during Battle of Tarawa, where he earned the Navy Cross, the United States military's second-highest decoration awarded for valor in combat.

After his company was almost wiped out, he had rallied the survivors of his unit, two M4 Sherman tanks and other Marines from infantry and machine gun platoons scattered on the beach, from which he formed a composite battalion and attacked.

Ryan, who had been thought to be killed in action, arranged for naval gunfire and mounted an attack that cleared the island's western end.

[5][6] Citation: The President of the United States of America takes pleasure in presenting the Navy Cross to Major Michael Patrick Ryan (MCSN: 0-6934), United States Marine Corps Reserve, for extraordinary heroism and distinguished service while serving as Commanding Officer of Company L, Third Battalion, Second Marines, SECOND Marine Division, and also as Commanding Officer of a Composite Battalion, in action against enemy Japanese forces at Betio Island, Tarawa Atoll, Gilbert Islands, from 20 to 24 November 1943.

Landing with his company in the fourth wave, Major Ryan courageously led a fierce, determined assault against the enemy and, retaining the initiative despite heavy casualties sustained by his forces, organized two other rifle companies with his own into a composite battalion which, under his skillful direction, successfully held a shallow beachhead throughout the remainder of the day and night.

On the following morning, he led his composite unit in an aggressive attack toward the strongly-defended south beach of Betio Island, continually exposing himself to intense hostile fire and inspiring his men by his own personal valor until an important beachhead was cleared of the Japanese and reinforcements and supplies could be landed for our forces without resistance.

Major Ryan's brilliant tactical ability and indomitable fighting spirit in the face of grave peril contributed in large measure to the ultimate capture of a highly strategic atoll and reflect great credit upon himself, his gallant command and the United States Naval Service.Following the end of the war, Ryan decided to remain in the Marine Corps.

Naval Mission as technical advisor for Venezuelan Marine Corps until June 1953, when he was ordered back to the United States.

He was ordered back to Headquarters Marine Corps in 1957 and attached to the Plans & Policies Section, Personnel Division, as assistant chief.

While in this capacity, he was promoted to the rank of brigadier general in January 1966 and subsequently assumed duties as assistant chief of staff (G-2) for plans and operations.

General Ryan remained in Quantico until May 1969, when he was transferred to Camp Lejeune, North Carolina, in order to assume command of the 2nd Marine Division.

With General Wilson's blessing, the planning process for the first Marine Corps Marathon began and the inaugural run took place on November 7, 1976.