Secretary of War Newton D. Baker approved the proposal, and recalled MacArthur saying that such an organization would "stretch over the whole country like a rainbow.

"[3] On 1 August 1917, the War Department directed the formation of a composite National Guard division, comprising units from 26 states and the District of Columbia.

[4] The 42nd Division was assembled in August 1917 at Camp Mills, New York, four months after the American entry into World War I.

The 42nd arrived at the Western Front of Belgium and France in November 1917, one of the first divisions of the American Expeditionary Forces (AEF) to do so, under the command of Mann, although he was soon to be replaced by Major General Charles T. Menoher, who remained in this position for the rest of the war.

[7] French officers had been attached to the 42nd at Lafauche, Rimaucourt, and Rolampont as instructors in trench warfare who "...seemed, from Menoher and MacArthur's view, to think more highly of the Rainbow's performance than did AEF commander General John Pershing and his Chaumont staff".

[11] As far as administration, supply, and discipline were concerned, the division was part of Major general Hunter Liggett's I Corps, A.E.F., but for combat and training purposes it was under Major General Georges de Bazelaire, of the French VII Army Corps, with each of the 42nd's regiments assigned to one of the French Divisions holding the sector.

[14] The 42nd took part in four major operations during the last four months of World War I: the Champagne-Marne, the Aisne-Marne, the Battle of Saint-Mihiel, and the Meuse-Argonne Offensive.

[18] The original version of the patch symbolized a half arc rainbow and contained thin bands in multiple colors.

[18] According to the division's official history, Colonel William N. Hughes Jr., who had succeeded MacArthur as chief of staff, was credited with modifying the design to a quarter arc in an attempt to standardize it.

[19][22] They also reduced the number of colors to just red, gold and blue bordered in green, to standardize the design and make the patch easier to reproduce.

To emphasize the 42ID's continued lineage from the 42ID of World War I, division commander Major General Harry J. Collins issued the orders that activated the unit on 14 July, the eve of the twenty-fifth anniversary of the Champagne-Marne campaign in France.

Beginning in the latter month, "when the initial age rules began to have a substantial effect" on manpower utilization, and until September, the division lost 3,936 infantrymen, 840 field artillerymen, and 45 cavalrymen.

On 14 October 1944, the three infantry regiments were alerted for imminent overseas movement, and the entire division was restricted to Camp Gruber.

The disruption caused by the withdrawal of personnel and advancement of readiness dates meant that the division did not get the chance to participate in major division-versus-division maneuvers.

[25] As part of the Seventh Army's VI Corps, TF Linden entered combat in the vicinity of Strasbourg, relieving elements of the 36ID on 24 December 1944.

[25] While defending on a 31-mile sector along the Rhine north and south of Strasbourg in January 1945, TF Linden repulsed a number of enemy counterattacks at Hatten and other locations during the German "Operation Northwind" offensive.

During the ensuing struggle, one company of the 222nd Infantry was surrounded, but withdrew from their position and infiltrated back through the Germans to the regimental lines after exhausting all but 35 rounds of ammunition.

[25] During the night of 27 February, elements of the German 6th Mountain Division were withdrawn under cover of heavy artillery and mortar fire and replaced by the 221st Volksgrenadier Regiment.

[27] The 42ID attacked through the Hardt Forest during 15 to 21 March, broke through the Siegfried Line, and cleared Dahn and Busenberg, while Third Army created and expanded bridgeheads across the Rhine.

[28] In mid-May, 42nd Division patrols arrested German war criminal Arthur Greiser and Waffen-SS officer Heinz Reinefarth.

42ID units from the New Jersey Army National Guard provided security at all the major river crossings into New York City and Newark International Airport in the months following 11 September 2001.

The 2nd Battalion, 113th Infantry deployed to Guantanamo Bay as well and provided security for the Joint Task Force at Camp Delta.

Soldiers conducted combat actions and raids, seized weapons caches, destroyed improvised explosive devices (IEDs), trained Iraqi army forces, and worked on reconstruction to ensure free elections.

Maj. Gen. Joseph J. Taluto, commanding general of the division during its deployment, commended the many contributions of the 42ID led Task Force Liberty.

Vice Chief of Staff of the Army (VCSA), Gen. Richard Cody, saluted members of the 42ID at the unit's homecoming ceremony.

Premobilization training began in 2007 and took place in New Jersey, with further OIF specific preparation conducted at other Army installations out-of-state.

In 2008, the 27th Infantry Brigade Combat Team (IBCT), headquartered in Syracuse, New York, was mobilized and deployed to Afghanistan to train Afghan National Army (ANA) and police forces.

Staff Sergeant Alberto B. Martinez, from the officers' unit, was charged in the killing but was acquitted in a court-martial trial at Fort Bragg, North Carolina, on 4 December 2008.

Subsequently, Siobhan Esposito and Barbara Allen, the widows of the officers, continued to pursue justice for their husbands' deaths, pushing for the military to strictly enforce regulations that prohibit threats against superiors and require soldiers to report violations of "good order and discipline.

The 2–102nd Armor and the 1–114th Infantry were called to active duty and the combined unit was dispatched to Louisiana to provide security for FEMA.