William K. Harrison Jr. was born on September 7, 1895 in Washington, D.C. as the son of Naval officer and future Medal of Honor recipient, William Kelly Harrison and his wife Kate Harris.
He was a direct descendant of President William Henry Harrison.
Following high school, William Jr. received an senatorial appointment from Texas to the United States Military Academy at West Point, New York in May 1913.

He was a member of the class, which produced more than 55 future general officers including two Army Chiefs of Staff (Joseph L. Collins and Matthew B. Ridgway).
Among his classmates were: Clare H. Armstrong, Rex W. Beasley, Robert M. Bathurst, Henry A. Barber Jr., William O. Butler, Theodore E. Buechler, Homer C. Brown, Aaron Bradshaw Jr., John T. Bissell, Mark W. Clark, John T. Cole, Miles A. Cowles, Gerald A. Counts, Norman D. Cota, Joseph L. Collins, John W. Coffey, James A. Code Jr., John M. Devine, William F. Daugherty, William W. Eagles, Charles H. Gerhardt, Theodore L. Futch, Robert W. Hasbrouck, Arthur M. Harper, Ernest N. Harmon, Horace Harding, Milton B. Halsey, Augustus M. Gurney, Edwin J. House, Joel G. House, Charles S. Kilburn, Laurence B. Keiser, Harris Jones, Harold R. Jackson, Frederick A. Irving, Harris M. Melasky, William C. McMahon, John T. Murray, Charles L. Mullins Jr., Bryant E. Moore, Daniel Noce, Harold A. Nisley, Matthew B. Ridgway, William O. Reeder, Onslow S. Rolfe, Thomas D. Stamps, Willis R. Slaughter, Stephen H. Sherrill, Herbert N. Schwarzkopf, Albert C. Smith, Joseph P. Sullivan, Edward W. Timberlake, George D. Wahl, George F. Wooley Jr., Sterling A. Wood, Raymond E. S. Williamson, Robert A. Willard and George H. Weems.

Harrison graduated with Bachelor of Science degree on April 20, 1917, shortly following the United States entry into World War I, and was commissioned second lieutenant in the Cavalry branch.
He was subsequently ordered to Camp Lawrence J. Hearn, California, where he joined 1st Cavalry Regiment.

He was subsequently ordered with the regiment to Douglas, Arizona, from which his unit participated in the guard duties on the Mexican Border.
Harrison reached consecutively the ranks of first lieutenant and Captain and returned to West Point Military Academy as an Instructor of French and Spanish languages.
While in this capacity, he also completed advanced languages courses in French and Spanish.

Harrison was later transferred to the 7th Cavalry Regiment at Fort Bliss, Texas and served with that unit until early 1923, when he was ordered to Washington, D.C. for duty on the staff of Army War College.
He was promoted to Major during his service there and left for the Philippines in 1925, where he was attached to the 26th Cavalry Regiment (Philippine Scouts) at Camp Stotsenburg on Luzon.

Following his return stateside in 1932, Harrison was attached to the 7th Cavalry Regiment at Fort Riley, Kansas.
While stationed at Fort Riley, he completed advanced course at Army Cavalry School there and served on the Cavalry Board and as Troop Commander with 9th Cavalry Regiment.

Harrison was ordered to the Army Command and General Staff School at Fort Leavenworth, Kansas in June 1936 and graduated one year later.
He then joined the faculty of the school and served as an instructor of tactics until September 1937, when he was ordered to the Army War College for instruction.

He graduated in July 1938 and joined the 6th Cavalry Regiment at Fort Oglethorpe, Georgia.
Harrison remained in that assignment until August 1939, when he was attached to War Plans Division, War Department General Staff in Washington, D.C. While in this capacity, he was promoted to lieutenant colonel on July 1, 1940.
William K. Harrison Jr. was born on September 7, 1895 in Washington, D.C. as the son of Naval officer and future Medal of Honor recipient, William Kelly Harrison and his wife Kate Harris. He was a direct descendant of President William Henry Harrison. Following high school, William Jr. received an senatorial appointment from Texas to the United States Military Academy at West Point, New York in May 1913.
He was a member of the class, which produced more than 55 future general officers including two Army Chiefs of Staff (Joseph L. Collins and Matthew B. Ridgway). Among his classmates were: Clare H. Armstrong, Rex W. Beasley, Robert M. Bathurst, Henry A. Barber Jr., William O. Butler, Theodore E. Buechler, Homer C. Brown, Aaron Bradshaw Jr., John T. Bissell, Mark W. Clark, John T. Cole, Miles A. Cowles, Gerald A. Counts, Norman D. Cota, Joseph L. Collins, John W. Coffey, James A. Code Jr., John M. Devine, William F. Daugherty, William W. Eagles, Charles H. Gerhardt, Theodore L. Futch, Robert W. Hasbrouck, Arthur M. Harper, Ernest N. Harmon, Horace Harding, Milton B. Halsey, Augustus M. Gurney, Edwin J. House, Joel G. House, Charles S. Kilburn, Laurence B. Keiser, Harris Jones, Harold R. Jackson, Frederick A. Irving, Harris M. Melasky, William C. McMahon, John T. Murray, Charles L. Mullins Jr., Bryant E. Moore, Daniel Noce, Harold A. Nisley, Matthew B. Ridgway, William O. Reeder, Onslow S. Rolfe, Thomas D. Stamps, Willis R. Slaughter, Stephen H. Sherrill, Herbert N. Schwarzkopf, Albert C. Smith, Joseph P. Sullivan, Edward W. Timberlake, George D. Wahl, George F. Wooley Jr., Sterling A. Wood, Raymond E. S. Williamson, Robert A. Willard and George H. Weems.
Harrison graduated with Bachelor of Science degree on April 20, 1917, shortly following the United States entry into World War I, and was commissioned second lieutenant in the Cavalry branch. He was subsequently ordered to Camp Lawrence J. Hearn, California, where he joined 1st Cavalry Regiment.
He was subsequently ordered with the regiment to Douglas, Arizona, from which his unit participated in the guard duties on the Mexican Border. Harrison reached consecutively the ranks of first lieutenant and Captain and returned to West Point Military Academy as an Instructor of French and Spanish languages. While in this capacity, he also completed advanced languages courses in French and Spanish.
Harrison was later transferred to the 7th Cavalry Regiment at Fort Bliss, Texas and served with that unit until early 1923, when he was ordered to Washington, D.C. for duty on the staff of Army War College. He was promoted to Major during his service there and left for the Philippines in 1925, where he was attached to the 26th Cavalry Regiment (Philippine Scouts) at Camp Stotsenburg on Luzon.
Following his return stateside in 1932, Harrison was attached to the 7th Cavalry Regiment at Fort Riley, Kansas. While stationed at Fort Riley, he completed advanced course at Army Cavalry School there and served on the Cavalry Board and as Troop Commander with 9th Cavalry Regiment.
Harrison was ordered to the Army Command and General Staff School at Fort Leavenworth, Kansas in June 1936 and graduated one year later. He then joined the faculty of the school and served as an instructor of tactics until September 1937, when he was ordered to the Army War College for instruction.
He graduated in July 1938 and joined the 6th Cavalry Regiment at Fort Oglethorpe, Georgia. Harrison remained in that assignment until August 1939, when he was attached to War Plans Division, War Department General Staff in Washington, D.C. While in this capacity, he was promoted to lieutenant colonel on July 1, 1940.
William Kelly Harrison Jr.