Donald Trump has selected retired Marine Gen. James “Mad Dog” Mattis to run the Department of Defense, the Washington Post reported on Thursday. A formal announcement from the Trump transition team is expected next week. Because Mattis is recently retired, his confirmation will also require Congress to pass a law ending of the prohibition against those who’ve served active duty within the last seven years from serving a civilian post. “General James ‘Mad Dog’ Mattis, who is being considered for Secretary of Defense, was very impressive yesterday,” the president-elect tweeted several weeks ago, after meeting with Mattis. “A true General’s General!” Following the Republican primary season, Mattis was frequently named as a possible candidate among “Never Trump” conservatives looking for an alternative to voting for Trump or Democratic candidate Hillary Clinton.