 Access to the Aegean and Marmara seas meant that the Ottomans could now implement the conquest of the southern Balkans, and could advance further north into Serbian Empire and Hungary.During the Byzantine civil war of 1352–57, Turkish mercenaries allied with the emperor John VI Kantakouzenos plundered most of Byzantine Thrace and, around 1352, were granted the small fortress of Tzympe near Gallipoli.On 2 March 1354, the area was struck by an earthquake that destroyed hundreds of villages and towns in the area.