The Ottomans requested that he reconfirm his vassalage in addition to surrendering Silistra , at the time the most populous Bulgarian city along the Danube .
Ivan Shishman left Tarnovo and headed to Nikopol , where he was besieged and forced to ask for peace .
The Ottomans requested that Ivan Shishman reconfirm Ivan Shishman 's vassalage in addition to surrendering Silistra , at the time the most populous Bulgarian city along the Danube .
Ivan Shishman left Tarnovo and headed to Nikopol , where he was besieged and forced to ask for peace .