United States Army General. Born in Junction City, Kansas, the son of famed Indian fighter, Adna Romanza Chaffee, he graduated from West Point in 1906, ranking 31st in his class of 78 graduates. He was commissioned a Lieutenant of Cavalry in 1906 and won recognition as the "Army's finest horseman." His first tour of duty was with the 15th United States Cavalry as part of the Army of Cuban Pacification. He was then was assigned to the Mounted Services School at Fort Riley, Kansas from 1907 to 1911, where he commanded the mounted detachment serving the students and staff of the Army War College. He was also a member of American Equestrian Teams that competed world-wide. He attended a French Cavalry School for a year, returning to teach again at Fort Riley. He then served with the 7th Cavalry regiment in the Philippines from 1914 to 1915. In 1916, he was transferred to the Staff and Faculty at West Point as the Senior Cavalry Instructor in the Tactical Department, serving in this post until 1917. Having reached the rank of Captain, he served as the adjutant for the 81st Division as it prepared to depart for France during World War I. During the conflict, he served as an infantry Major with the IV Army Corps during the St. Mihiel offensive, and later promoted to the temporary rank of Colonel, he served with the III Corps throughout the Meuse-Argonne offensive. He returned to the United States in 1919, with his Regular Army rank of Captain of cavalry, to become an instructor at the Command and General Staff School at Fort Leavenworth. In 1920, he reached the rank of Major. During this period in his career he held a variety of positions with the 3rd Cavalry and IV Corps after his tour at Fort Leavenworth. He served with the 1st Cavalry Division in 1921 and remained at Fort Bliss through 1924. After attending the Army War College, he assumed command of a squadron of the 3rd Cavalry from 1925 to 1927, and that year he predicted that mechanized armies would dominate the next war. Following this command, he moved to the War Department's General Staff, was promoted to Lieutenant Colonel, and worked on developing the first mechanized and armored forces for the Army until 1931. In that same year, He left the General Staff to serve as the Executive Officer of the newly formed 1st Cavalry (Mechanized) at Fort Knox, Kentucky. In 1934, he returned to the War Department, where he served as the Chief of the Budget and Legislative Planning Branch. 1938 saw his return to Fort Knox to assume command of the 1st Cavalry (Mechanized). He was promoted to Brigadier General in November of that year and given the command of the 7th Mechanized Brigade, the Army's only armored force. He led the embryonic unit through crucial maneuvers conducted from 1939 to 1940. The Louisiana Maneuvers held in 1940, in particular, became noteworthy for the impact they had on developing United States mechanized doctrine. In June of that year, he was appointed the Commander of the Armored Force, responsible for integrating all branches of the Army into mechanized warfare. As such, he played a major role in the development and fielding of the 1st and 2nd Armored Divisions, with Bruce McGruder in charge of the 1st and George S. Patton in charge of the 2nd. Promoted to Major General in October 1940, he was given command of the I Armored Corps. He battled continuously during the prewar years for suitable equipment and for establishment of tank divisions. With the collapse of the French Army in June 1940, his 1927 predictions of the importance of armored forces in modern warfare were confirmed. Unfortunately, he would never live to see the major armored battles of World War II that changed the face of modern warfare forever. Overworked and suffering from cancer, he died in Boston, Massachusetts. He was known as the "First Chief of the Armored Force" (as proclaimed on his tombstone) and is known as "Father of the Armored Force" in military history.

Camp Chaffee, later Fort Chaffee, near Fort Smith, AR was named for him when it was established in 1941.