He was unable to compete in the 1941 Rose Bowl when the Nebraska National Guard was mobilized in December 1940 prior to World War II.

[1][2] By the spring of 1942, Greenlief had been promoted to company first sergeant and was accepted to attend Infantry Officer Candidate School at Fort Benning, Georgia.

He participated in the liberation of Saint-Lô during Operation Overlord, the Battle of the Bulge, and the American advance into Germany.

[5] Greenlief was a colonel when he began his career at the National Guard Bureau on January 1, 1960, as executive officer of the Army Division.

He served as chief of the Army Division from November 3, 1962, to September 13, 1963, as a brigadier general, and was succeeded by Charles L. Southward.

[9] In 1999 the Governor of Nebraska announced that Greenlief had received a state promotion to lieutenant general to acknowledge his long service and superior performance of duty.

[12][13] The Nebraska National Guard's facility in Hastings is named the Francis S. Greenlief Training Site.