So, from our own experience with this we already know what happened. As we know many buildings were connected to the northern chaos base, we shot all the turrets off it and reinforced the buildings. The next day chaos took down that northern terminal that was connected to all of these buildings, we know this because it was invulnerable with the 3 day timer that new terminals have. So what they did not know is when you break a connection from a terminal to a building it flags the building or buildings. It then flagged all the buildings with connection to this northern terminal (now taken down and put back up) and allowed them to be killed (as we learned from when they hit us.) So long story short they broke connection to the buildings it pvp flagged them and took away their reinforce, they are then able to be killed.