Encounter set:
Assault on Osgiliath
Osgiliath.
Action:
If there is no active location, search the encounter deck and discard pile for an Osgiliath location, reveal it and add it to the staging area. Then, make West Gate the active location. Shuffle the encounter deck.
Forced:
After the player who controls West Gate lets an attack go undefended, return West Gate to the staging area.