Sec. 4.
Using National Security Assets for Law and Order.
(a) Within 90 days of the date of this order, the Attorney General and the Secretary of Defense, in consultation with the Secretary of Homeland Security and the heads of agencies as appropriate, shall increase the provision of excess military and national security assets in local jurisdictions to assist State and local law enforcement.
(b) Within 90 days of the date of this order, the Secretary of Defense, in coordination with the Attorney General, shall determine how military and national security assets, training, non-lethal capabilities, and personnel can most effectively be utilized to prevent crime.
... Where 'crime' is defined as 'whatever the fuck the Trump admin decides is a crime, or whoever the fuck they decide is a criminal.'
This is about as direct as possible as it is to say 'the military will be engaging in domestic policing operations at scale and in depth.'
As other commenters have pointed out... 'national security assets' means... personnel of all kinds, guns, ammo, tanks, helicopters, jet aircraft... logistics systems, military bases, naval vessels...
It is literally anything under the control of or used by the military, its the catch all term for 'everything, including the kitchen sink'.
This is like... hrm ok, we're gonna have a striker brigade company do security/presence patrols through Pittsburgh like it's Mosul or Baghdad, we're gonna have global hawks assisting chasing down suspects, we're gonna have some of the old barracks at the old training grounds retrofitted into detention centers, or maybe we'll just use engineering companies to set up some new concentration camps...
Yeah, all of that kind of shit is now on the table, being considered.
If an actual, 'classical' civil war of military vs military is gonna start, this would be how.