Reviewed turn 265 save and some others around there. Interesting fact is all city defenders are gone from New Hallas even though they were there when I originally saved. I went back and looked at turn 150 - appropriate # of city defenders there.
So in short, something occurred around turn 275 (I finished building an armorer) and then all of a sudden all city defenders gone... however, going back and reloading a turn 265 savegame loads New Hallas with 0 city defenders even though I know for a fact they were all there when I originally saved on 265.
Went ahead and demolished all city improvements at turn 265. Ended turn to see what would happen, none came back.
Very odd. Regardless, will call this playthrough since I can't fix the city defenders.
Oh well, time to start another game.