In the spring of 1393 the son of Ottoman Sultan Bayezid I, Suleyman Çelebi, laid siege to the Bulgarian capital Tarnovo with his sizable forces. With Tsar Ivan Shishman out of the city (leading the remnants of his troops to the fortress of Nikopol), Euthymius was the one entrusted with the defense of Tarnovo. After a three-month siege on 17 July 1393, the Ottomans captured the capital despite its ferocious resistance; Gregory Tsamblak several years later suggested the conquest was due to treason from one of the non-Christian neighborhoods of Tarnovo.