Southern Defense Command

Southern Defense Command (SDC) was established on 17 March 1941 as the command formation of the U.S. Army responsible for coordinating the defense of the Gulf of Mexico coastal region of the United States. A second major responsibility of SDC was the training of soldiers prior to their deployment overseas. The first Commanding General of SDC was Lieutenant General Herbert Brees, who continued on in command of the Third U.S. Army. SDC headquarters was co-located with the existing Third Army headquarters at Fort Sam Houston. SDC's operational region covered the states of New Mexico, Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Alabama, Tennessee, and the western half of the Florida Panhandle.

Third U.S. Army was shipped to England in January 1944 where Lieutenant General George S. Patton, Jr. took over command from General Hodges. Major General Henry C. Pratt assumed command of Southern Defense Command.

In January 1945 Southern Defense Command was merged into Eastern Defense Command.