To be clear, the latest news is “intra-civilian” but is likely to cross over given the stakes.
Remember the old days where the “smart” Bolsheviks left the personnel and other boring issues to Stalin? Yeah, so Stalin staffed the new Soviet government with his guys, and the theorists, well, they did not end up this way. That might be too bloody of an example, but I am not at all surprised that General (retired) Mattis is having tensions with Michael Flynn and the other Trump folks over who to staff the Pentagon.
If Mattis can’t pick his own staff, it will mean not only that he will not have control over the building (the Pentagon), but he would have very little influence at National Security Council meetings. he would start the administration pre-neutered. I don’t know the guy, but all I have heard about him suggests that he won’t let that happen. Which means he gets his choices or he abandons ship (Marines are used to that kind of thing).
The SecDef job is one of the hardest jobs in government–having to manage the biggest budget, with the stakes being war, peace, victory, defeat, one of the largest bodies of personnel, etc. It requires a team of people who the SecDef trusts to manage procurement, take care of the personnel, and work with the rest of the interagency while he (could have been she…) advises the President on the use of force around the world. If Mattis has to work with Trump appointees that he does not like or trust, then he has lost before the battle has started.
I am sure this news has Vegas re-setting the over/under of how long Mattis will last. Whatever it is, I am tempted to bet the under. We shall see how daring/stupid Flynn/Bannon and others driving this clash are, and we will learn if Mattis is willing to accept being a symbolic SecDef.