Christopher C. Miller began his military career in 1983 as an enlisted Infantryman before becoming a commissioned Infantry officer in 1987. He later transferred to Special Forces and served in multiple special operations organizations throughout his career. Miller has now been appointed as the acting US Secretary of Defense, which was unanimously confirmed by the Senate. He will be formally confirmed for the role in 2021.
Source: https://www.foxnews.com/politics/who-is-christopher-c-miller-acting-us-secretary-of-defense