The Burgundian and Wallachian army laid siege to Silistra in the middle of September, but they could not capture it. Before long, however, they conquered and destroyed the small fort at Tutrakan. Vlad convinced Wavrin to attack Giurgiu, saying that whenever the Ottomans "want to harry Wallachia or Transylvania, they and their horses can cross" the Danube near the fortified island at Giurgiu, connected to the Wallachian bank by a bridge. During the siege of Giurgu, two iron rings of a large bombard suddenly broke, killing two soldiers, because Vlad, who was in the command of the fire, did not allow the bombard to cool down between blows. The Ottoman garrison of the fortress capitulated on the condition that they were allowed to freely leave for the Ottoman Empire. However, after they left the fortress, 2,000 Wallachian soldiers attacked and massacred them at Vlad's order, because he regarded the commander of the Ottoman garrison responsible for his captivity in 1442.