The Greek Dark Age is the interval between the collapse of the Mycenaean civilization, around 1200 BCE, and the Greek Archaic Period, around c. 800 BCE. The Dark Age era begins with a catastrophic event: the collapse of the Mycenaean civilization, when all major Mycenaean regional centres fell out of use after suffering a combination of destruction and abandonment. Linear B script, the Mycenaean writing system, was lost shortly after c. 1200 BCE; for this reason, we have no first-hand written documents of any kind for this period. Thus, our understanding of the Greek Dark Age relies largely on archaeological research.
Iron-working is the one technological innovation that stands out during this period, so the Greek Dark Age is also known as the Early Iron Age. Iron-working was an innovation that seems to have been imported into Greece, not developed there, and it possibly reached Greece through Cyprus and the Near East. Metalworking methods during the Dark Age show signs of technical deficiencies in warlike items at several sites compared to earlier Bronze Age practices.
More than a century before the Mycenaean collapse, we find evidence suggesting that there were already conflict and instability in the Aegean. During the LH IIIA-B period (see Table 1), a fortification was built at Mycenae, protecting the palace and part of the residential space; some of the houses outside the citadel were destroyed during the LH IIIB period (accidental destruction cannot be outruled), and after this incident the fortification was extended and the water supply secured. Around this time, similar initiatives were undertaken in Athens, Tiryns, and Gla (Boeotia), and it is possible that a wall closing off the Isthmus of Corinth was built, presumably to control the only access by land to the Peloponnese. At least some of these events might be connected with the Egyptian and Hittite documents recording land and sea raiding activities around the same time.