The US Marines were half-way between the army and the Navy. The Marines were carved out of the army. The Space Force will mostly be taken from the Air Force but will include other existing space satellites and other space-related assets from other military branches.
The Pentagon will take three of the four components of the new Space Force:
* a new combatant command for space,
* a new joint agency to buy satellites for the military
* a new warfighting community that draws space operators from all service branches.
These changes are what can be done before congressional approval.
Creating services and support functions (financial management and facilities construction) will require congressional funding and authorization.