How did the Trojan war affect Greece?
However there is another theory about the Greek decay just after the war. It is based on this mystery: The greeks wanted Troy because it controlled a valuable trade passing (and not for Helen as it is written on the myth), they spent much effort in sieging and when they finally conquered it, they left without establishing their rule. This mysterious act could be explained by historical references of an eastern barbarian horde, which was invading and destroying the civilizations of the middle-east. Maybe the greeks left Troy to prepare their defences against them and since their economy was based on trading with the middle-easterns, their socities decayed because of the invasion of these countries by the barbarian horde.