Donald Trump intends to nominate Gen. James Mattis, one of the most respected military men of his generation, to run the sprawling Department of Defense, it was reported Thursday.

Citing people familiar with the decision, the Washington Post said the announcement from the president-elect is expected next week.

But since a law prevents those on active duty within the last seven years from serving in a civilian post, Congress will not only have to confirm Mattis but also pass a law making an exception.

Congress has done that just once, when Gen. George C. Marshall was appointed to the post in 1950.

Mattis left the Marines in 2013 and has since been a think-tank scholar at Stanford’s prestigious Hoover Institution and a board member of several private companies.

Trump met with the general two weeks ago and expressed praise for him the next day.

“General James ‘Mad Dog’ Mattis, who is being considered for Secretary of Defense, was very impressive yesterday. A true General’s General!,” the president-elect tweeted.

The Trump campaign did not respond to a request for comment.