Haislip was born in Woodstock, Virginia on July 9, 1889, and moved at age 2 to Staunton, Virginia. He was commissioned a second lieutenant of infantry upon graduating from the United States Military Academy at West Point in 1912.

Haislip served in Vera Cruz, Mexico in 1914 after the Tampico Affair. From 1917 to 1921, he served with the American Expeditionary Forces, first in World War I, then in the occupation of Germany. During his time overseas his assignments included being on the General Staff of V Corps; Division Machine Gun Officer for the 3rd Division, and General Staff, U.S. Forces in Germany. During World War I he participated in the Battle of Saint-Mihiel and the Meuse-Argonne Offensive. He returned to West point as an instructor from 1921 to 1923. He next attended a series of schools, beginning with the U.S. Army Infantry School from 1923 to 1924, then the Command and General Staff School from 1924 to 1925, and finally going back overseas to attend the French Ecole Superieure de Guerre from 1925 to 1927. He returned to the United States as Assistant executive in the Office of Assistant Secretary of War from 1928 to 1931, followed by the Army War College from 1931 to 1932, and an assignment as an instructor at the Command and General Staff School from 1932 to 1936.

In World War II, he organized the 85th Infantry Division and served as commander from April 1942 to February 1943. He next took command of XV Corps and served with it through Normandy, France, Rhineland, and Central Europe campaigns. He became commander of Seventh United States Army, and was in that billet when World War II ended in August 1945.

Following the war he was on the Secretary of War’s Personnel Board from September 1945 to April 1946, and a senior member of the Chief-of-Staff’s Advisory Group from 1946 to 1948. Prior to his selection in 1949 as Vice Chief of Staff he was Deputy Chief-of-Staff for administration, 1948-49. He retired in 1951.

After retiring from active duty in 1951, Haislip went on to become Governor of the Soldier’s Home in Washington, D.C., a position he filled from 1951 to 1966.

Haislip died on December 23, 1971 at Walter Reed Army Medical Center after suffering a stroke, and was buried in Arlington National Cemetery. His wife, the former Alice Jennings Shepherd (1897–1987), whom he had married on July 14, 1932, was later buried beside him.