[1] Promotion to major came in September 1965, and Fillmore subsequently served as the executive officer of the 3rd Battalion, 1st Marines in the Vietnam War.

Following the war, Fillmore returned to Virginia and was assigned as assistant comptroller and then staff secretary at Headquarters, Fleet Marine Force, Atlantic in Norfolk.

Following this, Fillmore attended the Armed Forces Staff College in Norfolk from August 1969 until January 1970 and subsequently became an instructor at the Amphibious Warfare School in Quantico, Virginia.

Two years later, in June 1978, he became special assistant to the chief of staff, Supreme Headquarters, Allied Powers, Europe and transferred overseas.

After filling this post for two years, Fillmore once again returned to Norfolk and took the role of deputy chief of staff, plans, policy, joint exercises, CINCLANTFLT on July 13, 1982.