Mattis retired in March 2013, and the Defense Department nominated General Lloyd Austin to succeed him and eventually Austin would also follow Mattis's footsteps to serve as United States Secretary of Defense. Mattis served as the 26th Secretary of Defense under 45th President Donald Trump and Austin served as the 28th Secretary of Defense under the 46th President Joe Biden. As of January 27, 2021, both Mattis and Austin was the only former CENTCOM Commander to served as United States Secretary of Defense.