Overnight Defense: Pentagon insists Mattis, Trump 'completely aligned' on leaving arms treaty | Trump 'not satisfied' with Saudi explanation on Khashoggi | Kushner says US still 'fact-finding'

Happy Monday and welcome to Overnight Defense. I'm Rebecca Kheel, and here's your nightly guide to the latest developments at the Pentagon, on Capitol Hill and beyond.THE TOPLINE: A landmark arms control treaty credited with helping...