Describing the events of the Byzantine–Bulgarian wars, in the spring of 1304, Georgi Pahimer tells that following the flash advance of Tsar Svetoslav, during which the Bulgarians conquer the fortresses lining the South Black Sea coast all the way down to Sozopol, one of the Byzantine armies, headed by Michael Doukas Glabas Tarchaneiotes and despot Voisil, brother of Tsar Smilets of Bulgaria, commenced a counter-advance from the Byzantine city of Vize. Retreating from the Strandzha mountain, with the aim to regroup, Svetoslav fought a decisive battle at river Skafida (see Battle of Skafida). According to Pahimer's account of the battle, the bridge collapsed while the Byzantines tried to cross with no order whatsoever and thus the victory was secured for the Bulgarians. Taking into account the structural durability of the bridge, historians agree that its collapse was most likely planned and executed by the Bulgarians, lead by Tsar Theodore Svetoslav.