Strongholds are the place where campaign battles take place. When your nation have control it is the place where you sign up for battle and when it is under beast control it is the fortification you attack during campaign battle.
For hawk eye you need to go to an outdoor yagudo controlled area and click a ??? at the stronghold. Note that there are 2 ???s at each stronghold; one for the hawk eye Ops and one for the slaughterhouse Ops.
Bayan of Bahamut
The Monetary System is going down.
Get ready for the Scientific Method.