 In an effort to extort money from Mehmed, Constantine implicitly threatened to release Orhan Çelebi, Mehmed's cousin and the only other known living member of the Ottoman dynasty (and as such a potential rival to Mehed), who was held prisoner in Constantinople.The ill-advised threat gave Mehmed a "casus belli" and late in 1451, preparations were already underway for a new Ottoman siege of Constantinople.To prevent aid coming from the Morea, now governed by Thomas and Demetrios, Mehmed II sent one of his generals, Turahan Bey (who had raided the Morea twice before) to devastate the peninsula.