Why was there a collapse in authority in the Greek peninsula in the 7th century ?
From the 580s on , as attested in the " Chronicle of Monemvasia " , the Slavic invasions which affected the wider Balkans reached the peninsula , and led to the abandonment of the urban centres of Antiquity in favour of either remote or offshore locations like Monemvasia , while the inhabitants of several cities such as Patras are claimed by the " Chronicle " to have emigrated to Italy altogether .