Everyone, read this Politico story now for back story.
http://www.politico.com/story/2017/07/26/trump-transgender-military-ban-behind-the-scenes-240990
A band of House Republicans were upset that their ban on gender-reassignment surgery for the military was getting blocked in Congress, and also that Mattis didn't take their side. So they went directly to Trump and threatened to blow up funding for The Wall and the military if he didn't take their side. He went one further and announced he wanted to kick all trans people out of the military, which they weren't asking for.
Now there's more confusion in the deal, Mattis is pissed off, no one knows what to do next.
This whole transgender affair is starting to remind me a bit of the original Muslim ban debacle in late January. Making an abrupt and ill-prepared announcement which just creates a whole lot of chaos, because even officials
within the Trump administration are totally taken aback by it.
Unfortunately, Donald Trump has the habit of never backing down -
especially when he's criticized for something - so we're probably stuck with this mess.