President Trump is nominating four-star General Mark Milley to be Chairman of the Joint Chiefs of Staff, he announced in a tweet early Saturday. Milley, who’s presently chief of staff of the U.S. Army—replaces General Joe Dunford, who will retire, the president added. Dunford, who is with the U.S. Marines, will see an end to his term as Joint Chiefs chairman in the fall, according to The New York Times. Trump alluded Friday to the coming announcement during a conversation with reporters on Friday at the White House, saying something would emerge at Saturday’s Army-Navy football game. “I can give you a little hint: It will have to do with the Joint Chiefs of Staff and succession,” the president reportedly said. The other contender for the top military job appeared to have been Air Force chief of staff, Gen. David L. Goldfein. While it’s unusual for a president to pick the Joint Chiefs successor this far in advance of the present chair’s departure, Trump reportedly prefers Milley, who’s a fixture both in the Pentagon and military bases worldwide, the Times explained. Trump’s pick stands in conflict with Defense secretary Jim Mattis, who is thought to have favored Goldfein for the post. That Trump and Mattis disagree doesn’t come as a shock, as the President has repeatedly disregarded him on issues of late, such as sending U.S. troops to the U.S.-Mexico border, per the Times.