Just finished nightmare, tips is to totally ignore food. I starve myself all the way until i closed the portal. Just keep conquering apartment and recruit survivors. Of course the 2 mall conquered near the beginning really helps a lot. Make your way towards all the mall, it increases defense significantly and that free your soldiers to do the attacking. Have fun.
 "Rebuild"){kind=icon}
 "Homerun In Berzerk Land: Berzerk Ball"){kind=icon}
 "Demons Took My Daughter"){kind=icon}
 "Great Dungeon in the Sky"){kind=icon}