Caldwell was a top Hegseth adviser until he was escorted out of the Pentagon in April 2025 and fired in connection with the leak investigation. Two other top Pentagon officials, Darin Selnick and Colin Carroll, were removed in similar fashion. Caldwell, an Iraq War veteran who has known Hegseth for a decade and has deep ties to Arizona politics. Caldwell, a University of Arizona graduate, was born in California, The Marine Corps veteran worked for the congressional office and 2012 campaign of U.S. Rep. David Schweikert, R-Arizona. Caldwell first began working with Hegseth at Concerned Veterans for America, an advocacy group that pushed for reform after the 2014 Phoenix Veterans Affairs scandal. He also served as campaign manager for foreign policy initiatives at Stand Together.