I would require the establishment or capture of a Mediterranean port which would then require protection of one or more air bases and several perimeter ground bases. From there, it would require the constant engagement of ISIS with the intent to DESTROY them. Not to capture or contain. Decimation of their forces and any and all that support them. Collateral damage be damned.
This is NOT supported by left who will be screaming about how we are cowardly, cruel, unfair. etc. So the first battle will be for the will of the American people.
If we do that without the invitation of Assad, then we are invaders.
The Russians have a Naval Base and a Forward Operating Base with an airfield there. On top of that they are building an Army base.
Doing what you are talking about would have U.S. forces engaged with Syrian and Russian forces.