Ferdinand's army seized Visegrád, Vác, Pest, Tata and Székesfehérvár in October, but could not capture Buda. His military commander, Wilhelm von Roggendorf, again laid siege to Buda on 4May 1541. Suleiman left Istanbul at the head of a large army in June to take advantage of the new civil war in Hungary. On his command, Petru Rareș, Prince of Moldavia, captured Stephen Majláth and forced the Transylvanian Diet to swear fealty to John Sigismund in late July. Roggendorf lifted the siege of Buda before Suleiman reached the town on 26August.