Collins took part in the occupation duties in Kyushu and upon the departure of 5th Marine Division to the United States in November 1945, he remained in Japan and was transferred to 2nd Marine Division.
Collins joined 6th Marine Regiment under Colonel Jack P. Juhan as Regimental Military Governor in Fukuoka.
Collins was later appointed Regimental executive officer and returned to the United States in September 1946.

Upon his return stateside, Collins was ordered to San Diego, where he served as Inspector-Instructor of the 11th Reserve Tank Battalion.
He was responsible for the training of Marine Corps Tank reservist until August 1948, when he was ordered for Senior Course to the Marine Corps Schools, Quantico.
Collins completed the course in May 1949.
He then served as operations officer and instructor within Combined Arms Section, Marine Corps Educational Center, Quantico.
Collins later served as chief of staff, Landing Assault Section, Landing Force Development Center Quantico and was promoted to the rank of colonel in February 1951.

Collins was ordered for instruction to the National War College in Washington, D.C., in August 1951 and completed the course in June of the following year.
He was then transferred to London, England and attached to the Joint American Advisory Group.
Shortly afterward, Collins was transferred to Frankfurt, Germany and attached to the Headquarters of newly activated United States European Command under General Matthew Ridgway.
He served as Staff Operations Officer, Policy Branch, Operations Division until August 1954, when he was ordered back to the States.

He returned to well known Marine Corps Educational Center, Quantico as a member of Advanced Research Group, which was tasked with the development of the recommendations on how the MAGTF should evolve structurally to meet the challenges of atomic warfare and new technologies such as helicopters and jet aircraft.

In August 1955, Collins was transferred to Camp Lejeune, North Carolina as commanding officer of 2nd Marine Regiment, 2nd Marine Division under Major General Reginald H. Ridgely.
Colonel Collins supervised the landing exercise of regiment at Vieques, Puerto Rico, during the beginning of 1956.

Collins was then transferred to the staff of 2nd Division as assistant chief of staff for operations, before he assumed duties as divisional chief of staff during Operation Deep Water in September 1957, NATO naval exercise held in the Mediterranean Sea that simulated protecting the Dardanelles from a Soviet invasion.
He left 2nd Marine Division in May 1958 and assumed brief duties within Personnel Board at Headquarters Marine Corps.
He was ordered to the staff of Marine Corps Schools, Quantico one month later and served as president of Marine Corps Tactics and Techniques Board within Landing Force Development Center.

A highlight of his career came in November 1959, when he was promoted to the rank of brigadier general and appointed director of the Development Center.
He remained in that capacity until February 1961, when assumed duty as chief of staff, Joint Task Force 4, Atlantic Command at Fort Monroe, Virginia.
During the Cuban Missile Crisis in October 1962, Collins was transferred to Guantánamo Bay, Cuba, and commanded all Marine Ground Forces for eight weeks.
He then served as Task Force commander from August to November 1963 and meanwhile received Master of Arts Degree at George Washington University in June 1963.

He was appointed deputy chief of staff, Atlantic Command under Admiral Harold P. Smith in December 1963, and while in this capacity, Collins was promoted to the rank of major general on January 1, 1964.
For his service during Cuban Crisis and with Atlantic Command, Collins received newly established Joint Service Commendation Medal.
Collins took part in the occupation duties in Kyushu and upon the departure of 5th Marine Division to the United States in November 1945, he remained in Japan and was transferred to 2nd Marine Division. Collins joined 6th Marine Regiment under Colonel Jack P. Juhan as Regimental Military Governor in Fukuoka. Collins was later appointed Regimental executive officer and returned to the United States in September 1946.
Upon his return stateside, Collins was ordered to San Diego, where he served as Inspector-Instructor of the 11th Reserve Tank Battalion. He was responsible for the training of Marine Corps Tank reservist until August 1948, when he was ordered for Senior Course to the Marine Corps Schools, Quantico. Collins completed the course in May 1949. He then served as operations officer and instructor within Combined Arms Section, Marine Corps Educational Center, Quantico. Collins later served as chief of staff, Landing Assault Section, Landing Force Development Center Quantico and was promoted to the rank of colonel in February 1951.
Collins was ordered for instruction to the National War College in Washington, D.C., in August 1951 and completed the course in June of the following year. He was then transferred to London, England and attached to the Joint American Advisory Group. Shortly afterward, Collins was transferred to Frankfurt, Germany and attached to the Headquarters of newly activated United States European Command under General Matthew Ridgway. He served as Staff Operations Officer, Policy Branch, Operations Division until August 1954, when he was ordered back to the States.
He returned to well known Marine Corps Educational Center, Quantico as a member of Advanced Research Group, which was tasked with the development of the recommendations on how the MAGTF should evolve structurally to meet the challenges of atomic warfare and new technologies such as helicopters and jet aircraft.
In August 1955, Collins was transferred to Camp Lejeune, North Carolina as commanding officer of 2nd Marine Regiment, 2nd Marine Division under Major General Reginald H. Ridgely. Colonel Collins supervised the landing exercise of regiment at Vieques, Puerto Rico, during the beginning of 1956.
Collins was then transferred to the staff of 2nd Division as assistant chief of staff for operations, before he assumed duties as divisional chief of staff during Operation Deep Water in September 1957, NATO naval exercise held in the Mediterranean Sea that simulated protecting the Dardanelles from a Soviet invasion. He left 2nd Marine Division in May 1958 and assumed brief duties within Personnel Board at Headquarters Marine Corps. He was ordered to the staff of Marine Corps Schools, Quantico one month later and served as president of Marine Corps Tactics and Techniques Board within Landing Force Development Center.
A highlight of his career came in November 1959, when he was promoted to the rank of brigadier general and appointed director of the Development Center. He remained in that capacity until February 1961, when assumed duty as chief of staff, Joint Task Force 4, Atlantic Command at Fort Monroe, Virginia. During the Cuban Missile Crisis in October 1962, Collins was transferred to Guantánamo Bay, Cuba, and commanded all Marine Ground Forces for eight weeks. He then served as Task Force commander from August to November 1963 and meanwhile received Master of Arts Degree at George Washington University in June 1963.
He was appointed deputy chief of staff, Atlantic Command under Admiral Harold P. Smith in December 1963, and while in this capacity, Collins was promoted to the rank of major general on January 1, 1964. For his service during Cuban Crisis and with Atlantic Command, Collins received newly established Joint Service Commendation Medal.
William R. Collins