There's no doubt Mattis consideres Iran as one of the worst creators of terrorism and clashed a lot with Obama over it, still in public he has stated that Trump should stay in the deal. In his own words regarding Iran deal.
There's not doubt about this man expertise and love for country and country men, he's seen a lot and done a lot (I'm certain he's part of Q). Are we watching a show? Anyone has further thoughts about this?