At the outbreak of World War II, the 104th Infantry Division began preparing to participate in the war in Europe. The division was ordered into active military service on 15 September 1942 under the command of Major General Gilbert R. Cook, and was reorganized as the 104th Infantry Division at Camp Adair, Oregon. The 207th and 208th Infantry Brigades did not reactivate as part of an army-wide elimination of brigade commands within its divisions. The division was instead centered on three infantry regiments; the 413th, the 414th, and 415th Infantry Regiments.