The 40th Infantry Division ("Sunburst Division")^[2] is a modular division of the California Army National Guard. Following the Army's modularization in the mid-2000s, the division has become a modular unit consisting of three brigade combat teams, with National Guardsmen from throughout the Pacific and Western United States and Oceania. Its division headquarters is located at Los Alamitos Joint Forces Training Base in Los Alamitos, California.

After seeing service in World War I as a depot division, it was reorganized as the National Guard division for California, Nevada, and Utah, before seeing service in the Pacific Theatre of World War II. Later, the division served in Korea and some of its units were designated for Vietnam. The division was later reorganized redesigned as a National Guard unit completely within California. Later reorganizations included units from other states. The division was called up to quell civil disturbances and rioting that occurred during the Watts Riots in 1965, rioting during the Long, Hot Summer of 1967 and during the LA riots in 1992. Most recently, the division has been deployed overseas as part of the ongoing Global War on Terrorism, seeing service in Iraq and Afghanistan. As currently configured, the 40th Infantry Division has oversight and responsibility for the training and readiness of units in California, Oregon, Hawaii, Arizona, Washington, Alaska, New Mexico, Indiana, Nebraska, Nevada, Mississippi, Utah, Guam, and the Northern Mariana Islands.