After the death of John Szapolyai in 1540, Ferdinand's inheritance was robbed, given instead to John's son, John II Sigismund. Attempting to enforce the treaty, the Austrians advanced on Buda where they experienced another defeat by Suleiman; the elderly Austrian General Rogendorf proved to be incompetent. Suleiman then finished off the remaining Austrian troops and proceeded to "de facto" annex Hungary. By the time a peace treaty was enforced in 1551, Habsburg Hungary had been reduced to little more than border land. In 1552 the forces of the Ottoman Empire led by Kara Ahmed Pasha laid siege on the Castle of Eger, located in the northern part of the Kingdom of Hungary, but the defenders led by István Dobó repelled the attacks and defended the castle of Eger. The siege of Eger (1552) become an emblem of national defense and patriotic heroism in Hungary's occupations