One of the most modular division of the United States Army is the 40th Infantry Division. Also known as the Sunshine Division, this division of the U.S. Army is the one that had undergone modularization where it is it popular for its four brigade combat team having national guardsmen covering all the sides of the Pacific coast of the United States throughout all of the Oceania. The 40th Infantry Division has its headquarters in Los Alamitos, California and is known as the Los Alamitos Joint Forces Training Base. The division has served in both World War I (WWI) and World War II (WWII). In WWI it functioned as a depot division. Besides, has served as the National Guard division in states like Nevada, California and Utah. It has also served in Korea and in Vietnam though it completely served as the National Guard unit in California after it was redesigned and reorganized. Currently, the 40th Infantry Division is taking care of training and overseeing of many units in various states like the Guam, Alaska, Hawaii, Washington, Nebraska, Oregon, New Mexico, Arizona, Nevada, Utah, Northern Mariana Islands and Indiana.

Though the 40th Infantry Division was ready to put into service as the National Guard division during 1917 in some of the states like California, Utah, and Nevada, it didn’t happen. But in 1918 it was re-designated to serve as the depot division while receiving significant training and equipment. During WWI the division got placed in France and was put in service as depot division to supply new troops to the combat divisions.  However, before the end of WWI, the division provided over twenty-seven thousand replacements to many of other divisions. Though the 40th Infantry Division did not directly take part in the WWI combat, many personnel from the division took part in the WWI receiving Medals of Honor.

The 40th Infantry Division came to the forefront again during the WWII. Before it gave an entry into the war field, it got reorganized to a three regiment division having converted from a square 2 brigade and four regiment division. Its first duty was to serve as a defense for the islands in the outer Hawaii. Though its defensive positions were much improvised and well maintained it received continuous training while being on the assignment. Initially, the division took defense position and relieved the 24th Infantry Division in the North Sector. Later it went through intensive training and was its first combat assignment. However, the division did not enter into major battles because of natural obstacles like rain and mud.

The 40th Infantry Division also played a role in the Korean War after taking substantial training from Japan in 1951. In 1952, it moved to North Korea, and it relieved the 24th Infantry Division fighting in the battle front. Not limited to this, the 40th Infantry Division also fought in the battles of Heartbreak Ridge and Sandbag Castle. Unfortunately, the division suffered from causalities, and hence after returning from the war, it got reorganized and got named as the 40th Armored Division.