Following World War I, the National Defense Act of 1920 created the authority to form the 45th Infantry Division from the four states of Oklahoma, Colorado, Arizona and New Mexico.  The division was organized in 1923, and Oklahoma members camped together for the first time at Fort Sill, Oklahoma, in 1924.

In the period pre-dating World War II, the division was called upon to maintain order in times of disasters and keep peace during periods of political unrest. Governor John C. Walton used the Guard to prevent the Legislature from meeting when they were preparing to impeach him in 1923. Governor William H. Murray’s calls to duty included the enforcement of closing of banks and keeping open a free bridge on the Red River, in spite of a federal court order that it not be opened.

In September of 1940 the division was ordered into federal service for one year to engage in a training program. The division’s time in federal service began at Ft. Sill, and at the end of the first year they had participated in the Louisiana Maneuvers. By the end of the year the world situation had worsened, and the Thunderbirds continued their training and prepared for war.

The Thunderbirds trained at Fort Sill, OK; Camp Barkeley, TX; Fort Devens, MA; Pine Camp, NY; and Camp Pickett, VA. They had trained hard for their part in World War II, and on July 10, 1943 the division participated in their first of four amphibious landings. In all the division served 511 days in combat; fighting their way across Sicily, Italy, France, and Germany. The National Guard Division of the southwest became highly regarded by both regular army forces and the enemy for their valiant efforts and fighting abilities.

The 45th Infantry Division served with General George S. Patton’s U.S. 7th Army during the Sicilian campaign, and when the fighting was done, the commander had this to say about the division, “Your division is one of the best, if not the best division in the history of American arms.”

Following World War II the division reverted back to National Guard status, and the 45th Infantry Division became an all-Oklahoma organization. Weekly evening drill periods were again held in armories statewide, and Fort Sill was the site of their annual summer encampment.

In June of 1950 South Korea was invaded by North Korea this action led to the second federal mobilization of the 45th Infantry Division. The Thunderbirds were one of only two National Guard divisions to see combat in the Korean War; the other being the 40th of California.

Training for Korea began at Camp Polk, and in March of 1951 the division shipped out for Hokkaido, Japan for a continuation of their training. The move to Korea was made in December, 1951. The division served in the Yonchon-Chorwon area, and in sectors fronting Old Baldy, Pork Chop Hill, Heartbreak Ridge, and Luke’s Castle. The majority of the Oklahoma’s Guardsmen began returning to the States in the spring of 1952, but the division remained in Korea until the end of the conflict in 1953. In all the 45th Division saw 429 days in battle, participating in 4 campaigns.

After Korea the division reverted to their stateside status as a National Guard unit with reorganization in 1959 changing the structure of the division from a triangular to a pentomic division. The pentomic division was made up of 5 battle groups, each smaller than a regiment, but larger than a battalion. In January 1969 the 45th Infantry Division was disbanded. The former division was restructured into an infantry brigade, an artillery group, and a support command, with state headquarters providing general administrative and logistical support. This did not mean the end of the Thunderbird; the Thunderbird patch was retained by all the organizations, with the exception of the state headquarters, which continued to be identified with the Indian-head patch.