Krulak was assigned duty as the deputy director of the White House Military Office in September 1987. While serving in this capacity, he was selected for promotion to Brigadier general (United States) in November 1988. He was advanced to that grade on June 5, 1989, and assigned duties as the commanding general, 10th MEB/Assistant division commander, 2nd Marine Division (United States), Fleet Marine Force Atlantic, at Marine Corps Base Camp Lejeune, North Carolina on July 10, 1989. On June 1, 1990, he assumed duties as the commanding general, 2nd Marine Logistics Group Group/Commanding general, 6th Marine Expeditionary Brigade, Fleet Marine Force Atlantic and commanded the 2d FSSG during the Gulf War. He served in this capacity until July 12, 1991, and was assigned duty as assistant deputy chief of staff for manpower and reserve affairs (personnel Management/Personnel Procurement), Headquarters Marine Corps on August 5, 1991. He was advanced to major general (United States) on March 20, 1992. Krulak was assigned as commanding general, Marine Corps Combat Development Command, Quantico, on August 24, 1992, and was promoted to lieutenant general (United States) on September 1, 1992. On July 22, 1994, he was assigned as commander of Marine Forces Pacific/commanding general, Fleet Marine Force Pacific, and in March 1995 he was nominated to serve as the Commandant of the Marine Corps. On June, 29, he was promoted to General (United States) and assumed duties as the 31st commandant on June 30, 1995. He was relieved on June 30, 1999, by General James L. Jones.
Question: How many months after Krulak was advanced to major general was he promoted to lieutenant general?
Answer: 6