World War I

Square Division example: 1940 US Infantry Division. On the far left can be seen two Brigades of two Regiments each

M1917 helmet worn by a Doughboy of the 91st Division in France in 1918

Constituted on 5 August 1917 at Camp Lewis, Washington, near Tacoma, the division, commanded by Major General Henry Alexander Greene, soon thereafter departed for England in the summer of 1918. In September 1918, the division's first operation was in the St. Mihiel Offensive in France. Serving under the U.S. Army's V Corps, the division, now commanded by Major General William Johnston Jr., fought in the Meuse-Argonne Offensive and successfully helped to destroy the German First Guard Division and continued to smash through three successive enemy lines.^[1][4]

Twelve days before the end of World War I, the division, as part of the VII Corps of the French Sixth Army, helped drive the Germans east across the Escaut River in the Battle of the Lys and the Escaut. The division was awarded separate campaign streamers for its active role in the Lorraine, Meuse-Argonne and Ypres-Lys campaigns.^[1][4]

In 1919, the 91st was inactivated at the Presidio of San Francisco.

The Division was composed of the following units:^{[5][6][7][8][9]}

• Headquarters, 91st Division
• 181st Infantry Brigade
  • 361st Infantry Regiment
  • 362nd Infantry Regiment
  • 347th Machine Gun Battalion ^[10]
• 182nd Infantry Brigade
  • 363rd Infantry Regiment
  • 364th Infantry Regiment
  • 348th Machine Gun Battalion
• 166th Field Artillery Brigade
  • 346th Field Artillery Regiment (75 mm)
  • 347th Field Artillery Regiment (4.7")
  • 348th Field Artillery Regiment (155 mm)
  • 316th Trench Mortar Battery
• 346th Machine Gun Battalion
• 316th Engineer Regiment
• 316th Medical Regiment
• 316th Field Signal Battalion
• Headquarters Troop, 91st Division
• 316th Train Headquarters and Military Police
  • 316th Ammunition Train
  • 316th Supply Train
  • 316th Engineer Train
  • 316th Sanitary Train
    • 361st, 36nd, 363rd, and 364th Ambulance Companies and Field Hospitals

Interwar period

After being reconstituted in 1921 as part of the Organized Reserves and being assigned to the state of California, the division then served as an administrative control center for the next 21 years.^[1][4]

World War II

As the early battles of World War II involving the United States were being fought, the division was reactivated at Camp White, Oregon on 15 August 1942, under the command of Major General Charles H. Gerhardt. After initial training at Camp White, the division participation in the Oregon Maneuver combat exercise in the fall of 1943.^[11][12]

Triangular Division example: 1942 U.S. infantry division. The brigades of the Square division have been removed, and there are three regiments directly under divisional control.

Order of battle

• Headquarters, 91st Infantry Division
• 361st Infantry Regiment
• 362nd Infantry Regiment
• 363rd Infantry Regiment
• Headquarters and Headquarters Battery, 91st Infantry Division Artillery
  • 346th Field Artillery Battalion
  • 347th Field Artillery Battalion
  • 348th Field Artillery Battalion
  • 916th Field Artillery Battalion
• 316th Engineer Combat Battalion
• 316th Medical Battalion
• 91st Cavalry Reconnaissance Troop (Mechanized)
• Headquarters, Special Troops, 91st Infantry Division
  • Headquarters Company, 91st Infantry Division
  • 791st Ordnance Light Maintenance Company
  • 91st Quartermaster Company
  • 91st Signal Company
  • Military Police Platoon
  • Band
• 91st Counterintelligence Corps Detachment

Men of Company C, 363rd Infantry Regiment, 91st Infantry Division, on the road just south of Pianoro, Italy, April 1945.

Then, the division, now under Major General William G. Livesay, departed for the European Continent on 3 April 1944. There, on the Italian Front, the 361st Regimental Combat Team was detached to participate in the battles for Rome and the Arno River. It became the first formation of the U.S. Fifth Army to reach the river. In September 1944, the division crossed the Sieve River, outflanked the famous Gothic Line, and captured the Futa Pass. For its part in combat, the division was awarded the North Apennines, Po Valley and Rome-Arno campaign streamers.

The division returned to the United States where it was inactivated at Camp Rucker, Alabama, in December 1945.^[1][4] Two members were awarded the Medal of Honor during the war, Roy W. Harmon and Oscar G. Johnson.^[13]

World War II statistics

Army Reserve

Standard organization chart for a training division

In December 1946, the 91st was reactivated at the Presidio of San Francisco as part of the U.S. Army Reserve. In 1959, the division was reorganized and redesignated as the 91st Division (Training). In 1993, the division was again reorganized and redesignated as the 91st Division (Exercise) and again in 1999 as the 91st Division (Training Support).^[1][4]

Its headquarters was at Parks Reserve Forces Training Area (PRFTA), Dublin, California,^[15] when the 2005 Base Realignment and Closure Commission recommended the Department of Defense relocate the 91st Division to Fort Hunter Liggett.^[4]

The four brigades of the 91st Division were redesignated as separate brigades:

• 1st Brigade (PRFTA) is now 5th Brigade, 75th Division.
• 2nd Brigade (Fort Carson) is now 5th Armored Brigade.
• 3rd Brigade (Travis AFB) is now the 402nd Field Artillery Brigade.
• 4th Brigade (Fort Lewis) is now 191st Infantry Brigade.

The 91st Division moved its headquarters to Fort Hunter Liggett on 1 May 2009, was reorganized and re-designated as the 91st Training Brigade (Operations) on 1 October 2009 and was then re-designated as the 91st Training Division (Operations) on 1 October 2010.^[1]