The fortress of Palamidi in Naplion fell from within.

Listening to Abduction by John Mack and in it the objectives of the grey aliens is recorded. Humans are being modified by gradually merging DNA. The offspring of these mergers have no idea that this is happening. This merging is to allow a species with a hive brain and other mental capabilities to be able to breath earth's air. Messages to their minds educate them and steer their activities subconsciously. Meanwhile, the fertility of existing humans is decreasing rapidly. New diseases are thinning us out. In only a few generations, pure humans will be gone and no one will figure out how it happened.