[2] The blue represents the infantry, the red the artillery, with the white completing the colors of the flag of the United States of America.

On 28 October 1918, the division's advance detachment moved to Camp Mills, New York, preparatory to movement overseas.

In 1926-27, the active associate concept was abandoned and many of the division’s inactive elements were organized as RAI units by mid-1927 in the First and Second Corps Areas.

When funds were available, the 18th Infantry Brigade and the division’s other active elements, which included the 9th Tank Company, 9th Ordnance Company, 9th Quartermaster Regiment, and 25th Field Artillery Regiment, held maneuvers and command post exercises at Camp Devens, during which the division headquarters was occasionally formed in a provisional status.

Under the new “triangular” tables of organization, the 9th Division was reactivated, less Reserve personnel, on 1 August 1940 at Fort Bragg, North Carolina, and assigned to the I Corps.

The 9th Infantry Division was among the first U.S. combat units to engage in offensive ground operations during World War II.

Sent to England for further training, the division landed on Utah Beach on 10 June 1944 (D-day plus 4), cut off the Cotentin Peninsula, drove on to Cherbourg Harbour and penetrated the port's heavy defenses.

Turning east, the 9th crossed the Marne, 28 August, swept through Saarlautern,[6] and in November and December held defensive positions from Monschau to Losheim.

Moving north to Bergrath, Germany, it launched an attack toward the Roer river, 10 December, taking Echtz and Schlich.

On 30 January the division jumped off from Monschau in a drive across the Roer and to the Rhine, crossing at Remagen, 7 March.

Presidential Unit Citations:[9] The 9th Infantry Division was reactivated on 15 July 1947 at Fort Dix, New Jersey and assumed a peacetime readiness and training role.

The 9th Division was reactivated on 1 February 1966, and arrived in South Vietnam on 16 December 1966 from Fort Riley, Kansas.

Faced with unrelenting physical hardships, a tenacious enemy and the region's rugged terrain, the Division established strategies and quantifiable goals for completing their mission.

[10] Division commanding generals were: Maj. Gen. George S. Eckhardt (February 1966 - June 1967), Maj. Gen. George G. O'Connor (June 1967 - February 1968), Maj. Gen. Julian Ewell (February 1968 - April 1969), Maj. Gen. Harris W. Hollis (April 1969 - August 1969) The infantry units that served with the 9th Infantry Division were: Other units included: One of the experimental units serving with the division was the 39th Cavalry Platoon (Air Cushion Vehicle) which used three of the specially designed hovercraft to patrol marshy terrain like the Plain of Reeds along the south Vietnamese/Cambodian border.

The MRF was often anchored near the South Vietnamese city of Mỹ Tho, or near the Division's Đồng Tâm Base Camp and they conducted operations in coordination with the Navy SEAL teams, the South Vietnamese Marines, units of the ARVN 7th Division and River Assault Groups.

Following the Tet offensive in 1968, General Westmoreland stated that the Division and the MRF saved the Delta region from falling to the People's Army of Vietnam forces.

[30] Initially the vision was to create three motorized brigades with three new types of infantry battalion:[31][32] The light attack battalions utilized the Fast Attack Vehicles (FAV - later re-designated the Desert Patrol Vehicle), essentially a Volkswagen-engined dune buggy with either a 40 mm Mk 19 grenade launcher or 12.7 mm M2 Browning machine gun.

The FAV was designed to provide highly mobile firepower that could attack the flanks of heavier mechanized units.

The assault gun companies were to be equipped with the Armored Gun System (AGS), but because of delays in the AGS program they were initially equipped with M901 ITVs Improved Tow Vehicles, then M551 Sheridan light tanks and later with Humvees with TOW missiles or Mk 19 grenade launchers.

[30] McGrath writes that the 9th Infantry Division was organized as follows in 1988:[42] In fiscal year 1989 Chief of Staff of the United States Army General Carl E. Vuono approved the conversion of the division's two combined arms battalions light to standard mechanized infantry battalions.

Army leadership at first decided that inactivating units would turn in all of their equipment at "10/20" standard, i.e. in ready and reusable condition.

As inactivation proceeded, elements and individual soldiers from the division were detached and deployed for service in the Gulf War.

All of the division's flags and heraldic items were moved to the National Infantry Museum at Fort Benning, Georgia following its inactivation.

[58] The 7th Infantry Division, previously inactivated, resumed service as an administrative headquarters at Joint Base Lewis–McChord in 2012.