Castellaw’s service in the Marines spanned 36 years. He was with the UN during the Siege of Sarajevo, commanded a U.S. joint force in the multi-national security and stability operation in East Timor, and served as the chief of staff for the U.S. Central Command. His last assignments on active duty were in the Pentagon where he oversaw Marine Aviation and the Marine Corps budget.
In 2008, he returned home to Tennessee where he is affiliated with several national security advocacy groups and is a teaching fellow at the University of Tennessee, Martin. Castellaw also serves on several boards, works with economic development organizations, and advises a number of corporations.