Thank you for the article, it’s cool stuff... I always wondered if some of these underground cities might have also been somehow need for environmental reasons aside from security reasons?. Be interesting to try and see what suspected environmental science claims about these particular timelines of some of these.
This one is one of the few which has a definite start date, assuming that much of it wasn't already in existence when the order was given (6000 apartments is a remarkable about of work getting done by a fairly small number of people with medieval infrastructure support (the food, the water) in the middle of nowhere. Many of these structures are found in Anatolia, and Robert Schoch (among others) has suggested that they continued to be expanded and extended, but that the original excavations go back to the Neolithic.