Well, kinda.  The tip of the spear would start out fighting its way to the surface and then attempt to drive deep into adventurer territory in an effort to break their strength and sow discord behind their "lines" through subterfuge, assassination, and seeding areas with amplified monsters.  I may even add a mechanism that would allow the growing of living dungeons.

The follow up groups would start taking less guarded forts and other places that Adventurers rely on for safe fall back points.

Way later, if it ever gets that far, there would be a large scale army clash that would be tailored to drawing out vast numbers of adventurers and cropping their numbers drastically.

The victory condition that stands now would be the reduction of the adventurer population by 98%.  Non-adventurers are not even a necessary target at present.

I have to admit, I had not actually intended the race war paradigm that ended up forming.  So, I may restructure that part or abandon it entirely.  I'm sticking with the monster PCs though.