The 37th Division was inducted into federal service at Columbus, Oh. as the 37th Division and moved to Camp Shelby, Miss., 20 Oct 40. The division participated in the V Corps Louisiana Maneuvers, 16-27 Jun 41, then went to Evans, La. where it was part of both the Aug and Sep 41 Louisiana Maneuvers. The division returned to Camp Shelby, Miss., 3 Oct 41 where it was redesignated the 37th Infantry Division, 1 Feb 42. It arrived at the Indiantown Gap Military Reservation, Pa., 18 Feb 42, then moved to the San Francisco Port of Embarkation, 11 May 42, departing 26 May 42 to arrive in the Fiji Islands on 11 Jun 42 and Guadalcanal 5 Apr 43. The division landed on Kokorana Island, Solomons on 21 Jul 43, and New Georgia Island on 22 Jul 43. It returned to Guadalcanal 9 Sep 43 and landed on Bougainville on 8 Nov 43. It landed at Huon Gulf, New Guinea 18 Dec 44 and Manus Island 22 Dec 44 enroute to the Philippines, where it assaulted Lingayen Gulf, Luzon on 9 Jan 45. The division arrived at the Los Angeles Port of Embarkation on 18 Dec 45 and inactivated at Camp Anza, Calif., same date.
The division arrived at Viti Levu in the Fiji Islands on 11 Jun 42 with the mission of both fortifying the islands and conducting intensive training. On 5 Apr 43 it moved to Guadalcanal where it continued training. The 14th Infantry was detached and landed on Banika Island in the Russell Islands Group 7 Jun 43, and a battalion from it and the 145th Infantry were attached to the 1st Marine Raider Regiment for operations on New Georgia Island. The remainder of the 145th and 148th Infantry arrived at Rendova, New Georgia 7 Jul 43 and engaged in heavy fighting for Munda Airfield under the 43rd Infantry Division. The 148th Infantry attacked Barley Ridge and then shifted its assault to Horseshoe Hill where it was surrounded 26 Jul-1 Aug 43 until the Japanese evacuated their positions. The 145th Infantry finished clearing Bartley Ridge 31 Jul 43, The rest of the division had arrived on New Georgia in the meantime on 22 Jul 43 and all elements reverted to its control, and Munda Airfield was finally seized 5 Aug 43. The division pushed across the island and conducted combat patrolling until returned to Guadalcanal 2-22 Sep 43. The newly assigned 129th Infantry, formerly the Espiritu Santo garrison force, moved up to join it as the division moved to Bougainville 5 Nov 43-12 Jan 44.
The 148th Infantry landed first on Bougainville 8 Nov 43 and was followed by the 129th Infantry on 13 Nov 43 and the 145th Infantry which landed 19 Nov 43. Relieving the Marines there, the division took over the area perimeter defense, constructed roads and bridges, conducted patrols, and repulsed eight Japanese divisional attacks during March 1944. These included the 8 Mar 44 counterattack on Hill 700 which drove a salient in the lines of the 145th Infantry which wasn't reduced until 13 Mar 44 after heavy combat; the main counterattack of 11 Mar 44 toward Piva Airfield which hit the 129th Infantry; and the 23 Mar 44 general counterattack which penetrated the lines of 129th Infantry before it was defeated. The latter marked the last Japanese offensive activity in the Solomons and the division cleared the Laruma Valley during April 1944. The division remained on Bougainville until 14 Dec 44, conducting construction and combat activity up to 11 Oct 44 when it began training for operations in the Philippine Islands.
The division moved to the Philippines via Huon Gulf, New Guinea and Manus Island, and landed against slight resistance at Lingayen Gulf, Luzon, 9 Jan 45. The 148th Infantry took San Carlos 10 Jan 45 and the division assembled and then advanced against strong Japanese opposition toward Clark Field and Fort Stotsenberg. The 145th and 148th Infantry reached the Culayo-Magalang line and the runways of Clark Field 26 Jan 45 and captured their objectives with the 129th Infantry on 31 Jan 45. The division then turned south toward Manila and the 148th Infantry reached it 4 Feb 45. After crossing the Pasig River the division began the house-to-house combat which slowly reduced the city, and on 23 Feb 45 the assault was begun on Intramuros after heavy artillery preparation. The 145th stormed the Quezon and Parian Gates while the 129th Infantry crossed the Pasig River in assault boats and stormed the Mint Building. The 148th Infantry cleared the Legislative Building and by 3 Mar 45 the division had secured Manila. The division then garrisoned it until 26 Mar 45 and conducted mopping up activity.
The 129th Infantry was detached to Bauang and attached to the 33rd Infantry Division 26 Mar-10 Apr 45. The 145th Infantry remained in Manila when the division moved to northwest Luzon for the offensive against Baguio and did not rejoin it until 2 Jun 45. The division commenced its drive 10 Apr 45 as the 129th and 148th Infantry attacked up Highway 9 and took Three Peaks on 11 Apr 45. Following the Battle for Hairpin Hill the 148th Infantry reached the Irisan River 17 Apr 45, but the ridges there were not cleared until 21 Apr 45 when the advance resumed. Mt. Mirador fell after heavy combat to the 129th Infantry on 26 Apr 45 and Baguio was overrun by the combined action of 334d and 37th Infantry Divisions the following day. The division was relieved by the 33rd Infantry Division and moved to San Jose 4 May 45 where it rested until 29 May 45. It then moved into the Balete Pass-Santa Fe area and attacked north on Highway 5, 31 May 45, the 129th Infantry capturing Aritao on 5 Jun 45. Bagabag fell to the 145th Infantry on 9 Jun 45, and the division pushed across the Cagayen Valley and took Cauayan 16 Jun 45 and Ilagan 19 Jun 45. Although the Luzon campaign was officially closed 30 Jun 45, the division continued to mop up and secure its area, and was collecting and processing Japanese prisoners when the war ended.