In late 1914, Reed was assigned as an inspector-instructor to the New Jersey National Guard in Newark.
Reed was successful in the role and elected major of the 4th New Jersey Infantry in 1916 (though he could not accept because it was a state commission, the governor issued the rank as an honor).
Upon beginning the build-up in 1916 for the United States' entry into World War I, Reed was placed on several inspector teams, observing mobilized National Guard units in Florida and Georgia.
By the end of the year Reed was a mustering officer, originally demobilizing New Jersey units, but by early 1917 he began recalling units.
In July he was made a temporary major and remained with the Guard until October when he was assigned to the Inspector General's Department in Washington, DC.

In May 1918, he was promoted to temporary lieutenant colonel and assigned as the inspector of the 7th Division at Camp MacArthur in Texas.
The unit deployed to France in September, and in October Reed became assistant inspector of the Second Army.
In February 1919, at the request of Major General Eli Hemlick, commander of Base Section Number 5 in Brest, France, he was transferred to the section.
Hemlick praised Reed, saying he "did more than any other staff officer to bring order out of the chaos that existed in the camp during the early days."
He was appointed to temporary colonel in May and moved to the American Expeditionary Forces Inspector General office after the base section closed.
He eventually became the inspector of the American Expeditionary Forces in France.
For his work, he received the Army Distinguished Service Medal.
In 1920, he returned to the United States and became a permanent lieutenant colonel in July.

Over the next seven years, Reed attended the School of the Line in 1921, the General Staff School in 1922, the Army War College in 1923, and the Naval War College in 1924.
He was then an instructor at the Naval War College until June 1928 when he was assigned as the executive officer of the 29th Infantry Division at Fort Benning, Georgia.
In May 1930, Reed was made a full colonel.
He received command of the 12th Infantry Regiment at Fort Howard in Maryland in January 1933.


Reed was in command until being detailed to the Inspector General's Department as executive officer in October 1934.
His investigations included Benjamin Foulois and the Army Air Force and accusations of bribery against Alexander E. Williams.
Reed was appointed Inspector General on 1 December 1935, replacing John F. Preston.
As inspector general, Reed requested an additional brigadier general for the department due to its rapidly increasing caseload in 1937.
The same year he was involved in identifying areas for manpower reductions in the army.
Reed also investigated various U.S. property and disbursing officers for embezzlement.
He toured until 23 December 1939 and retired 30 April 1940.
In April 1942 Reed was recalled to active duty as a member of the War Department Personnel Board.
In 1945, Reed received an oak leave cluster in lieu of a second Distinguished Service Medal "for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility."
He retired on 25 June 1946, and lived in Washington, DC until his death on 1 May 1956.
Reed is buried in Arlington National Cemetery.
In late 1914, Reed was assigned as an inspector-instructor to the New Jersey National Guard in Newark. Reed was successful in the role and elected major of the 4th New Jersey Infantry in 1916 (though he could not accept because it was a state commission, the governor issued the rank as an honor). Upon beginning the build-up in 1916 for the United States' entry into World War I, Reed was placed on several inspector teams, observing mobilized National Guard units in Florida and Georgia. By the end of the year Reed was a mustering officer, originally demobilizing New Jersey units, but by early 1917 he began recalling units. In July he was made a temporary major and remained with the Guard until October when he was assigned to the Inspector General's Department in Washington, DC.
In May 1918, he was promoted to temporary lieutenant colonel and assigned as the inspector of the 7th Division at Camp MacArthur in Texas. The unit deployed to France in September, and in October Reed became assistant inspector of the Second Army. In February 1919, at the request of Major General Eli Hemlick, commander of Base Section Number 5 in Brest, France, he was transferred to the section. Hemlick praised Reed, saying he "did more than any other staff officer to bring order out of the chaos that existed in the camp during the early days." He was appointed to temporary colonel in May and moved to the American Expeditionary Forces Inspector General office after the base section closed. He eventually became the inspector of the American Expeditionary Forces in France. For his work, he received the Army Distinguished Service Medal. In 1920, he returned to the United States and became a permanent lieutenant colonel in July.
Over the next seven years, Reed attended the School of the Line in 1921, the General Staff School in 1922, the Army War College in 1923, and the Naval War College in 1924. He was then an instructor at the Naval War College until June 1928 when he was assigned as the executive officer of the 29th Infantry Division at Fort Benning, Georgia. In May 1930, Reed was made a full colonel. He received command of the 12th Infantry Regiment at Fort Howard in Maryland in January 1933.

Reed was in command until being detailed to the Inspector General's Department as executive officer in October 1934. His investigations included Benjamin Foulois and the Army Air Force and accusations of bribery against Alexander E. Williams. Reed was appointed Inspector General on 1 December 1935, replacing John F. Preston. As inspector general, Reed requested an additional brigadier general for the department due to its rapidly increasing caseload in 1937. The same year he was involved in identifying areas for manpower reductions in the army. Reed also investigated various U.S. property and disbursing officers for embezzlement. He toured until 23 December 1939 and retired 30 April 1940. In April 1942 Reed was recalled to active duty as a member of the War Department Personnel Board. In 1945, Reed received an oak leave cluster in lieu of a second Distinguished Service Medal "for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility." He retired on 25 June 1946, and lived in Washington, DC until his death on 1 May 1956. Reed is buried in Arlington National Cemetery.
Walter L. Reed