I don't know whether this has been answered elsewhere as I am new to the game (having spent the last five months tracking one down!)
Can the Nazgul 'capture' cities and/or strongholds that are unoccupied by the Free Peoples? I wondered if they could 'blitz' those cities/towns worth one point that are often 'overlooked' by the Free Peoples player (well, at least in the couple of games my son and I have played so far).