Born of elements of the famous Hawaiian Division in 1941, the 25th was about two months old when Japanese planes launched their attack on Pearl Harbor, Oahu, on December 7, 1941. Division soldiers set up and manned defensive positions around Honolulu and the Ewa plains.

The 25th was then ordered to deploy to Guadalcanal to relieve U.S. Marines there. Only 31 days were required to accomplish the mission and earned the Division its official designation, "Tropic Lightning" (adopted as the official title of the Division on August 3,1953).

Division soldiers were then dispatched to the Solomon Islands, headed for New Zealandand New Caledonia. It was during this time that the Division shoulder patch of a lightning bolt superimposed on a taro leaf was adopted. From early January 1945 until June 30, 1945, the Division fought in the Philippines. At the end of the war, the Division moved to Osaka, Japan, where they performed occupation duty until 1950.

In July 1950, the Division moved to Korea and handed the North Korean Army its first major setback. After the armistice, the Division stayed as an occupation force until September 1954, then returned to Hawaii, concluding more than 12 years of duty in the Southwest Pacific and Asia. From then until early 1963, the 25th established and conducted extensive training programs in jungle warfare techniques and Asian languages. The 25th was the only counter-guerrilla trained division in the Army.

In early 1963, the Division sent soldiers to Vietnam in response to a request from the U.S. Military Assistance Command, Vietnam (MACV), marking the Division's initial participation in the conflict.

After returning from Vietnam in early 1971, the Division was reduced to one brigade with a strength of about 4,000 soldiers. In mid-1972, the 2nd Brigade was reactivated and troop strength was increased to about 12,000 soldiers. In February 1973, the 29th Brigade of the Hawaii Army National Guard and the 100 Battalion, 442nd Infantry of the U.S. Army Reserve were designated to serve as the Division's 3rd "roundout" brigade in case of national emergency. This relationship lasted until October 1986, when the Hawaii NationalGuard and Army Reserve assumed a partnership affiliation with the Division.

On March 1, 1992, U.S. Army Hawaii (USARHAW) was assigned to the 25th Infantry Division (Light), creating 25th ID(L) & U.S. Army , Hawaii. The new organization also assumed additional command of U.S. Army Support Command, Hawaii (USASCH), U.S.Army Law Enforcement Command (USALEC) and the 45th Support Group, which was redesignated the 45th Corps Support Group (Forward) on October 16, 1993. USASCH was designated as the U.S. Army Garrison, Hawaii (USAG-HI) on February 17, 1994.

In 1995, the Division underwent another reorganization and reduction because of defense downsizing. First Brigade and its direct support units were inactivated and moved to Fort Lewis, Washington, where they were again reactivated as a detached brigade of the 25th Infantry Division (Light).

Today the "Tropic Lightning" Division is composed of three infantry brigades (two in Hawaii; one at Fort Lewis), an aviation brigade, division artillery, a division support command, and a complement of separate battalions. The major ground reserve force for the U.S. Pacific Command, the "Tropic Lightning" Division trains in Japan, Korea, Thailand, the Philippines and Australia.

In January 1995 3,700 soldiers from the 25th Infantry Division (Light) deployed to Haiti to participate in peacekeeping operations in Operation Uphold Democracy. The Division's mission was two-fold--the Division staff assumed the role of the Multinational Force headquarters and members of the Second and Third Brigades became members of the United States Forces Contingent. The 25th Infantry Division (Light) officially left Haiti on 31 March 1995 when the United Nations Mission in Haiti assumed command.Approximately 500 soldiers from the Second Brigade remained as part of the United Nations Force until early June.