Shortly after taking the oath of office, President Donald Trump, signed the Congressional bill waiving Defense Secretary-designate, retired US Marine General James Mattis, to serve in the cabinet leading the Pentagon, according to TheHill.com. After Trump's signature, the US Senate confirmed Gen. Mattis by a 98-1 vote. Mattis retired from the military in 2013. The National Security Act of 1947 requires a seven-year waiting period before retired military personnel can assume the role of Secretary of Defense. Mattis is the second Secretary of Defense to receive such a waiver, after George Marshall.