Complex sentence: Before the final siege of Constantinople Mehmed ordered Ottoman troops to attack the Morea, the despots, Demetrios Palaiologos and Thomas Palaiologos, brothers of the last emperor, failed to send any aid.
Split into simpler sentences: Before the final siege of Constantinople Mehmed ordered Ottoman troops to attack the Morea. The despots, Demetrios Palaiologos and Thomas Palaiologos, brothers of the last emperor, failed to send any aid.