Senate will have the last word. And unless the Senate leadership uses the loophole that the last majority leader used, the waiver will be subject to a filibuster, best I see it.
The Democratic Senate harpooned Sen Tower from Texas back in the 80's, I seem to recall. Tink Bush I nominted him. No filibuster either. But he seemed a good choice. Cheney finally got the job.
If you look at Mattis' language, it sounds like Trump himself talking.
The troop looks good to this old warrior, and his last ten years or so have been heavily focused upon an area of the world that needs experience there.