At the beginning of the thirteenth century Byzantium was still one of the most influential states in the eastern Mediterranean, possessing two-thirds of the Balkans and almost half of Asia Minor. After the capture of Constantinople in 1204 during the Fourth Crusade, the most prominent and successful of the Greek rump states was the Empire of Nicaea, which managed to re-capture the city in 1261 and restore Byzantium. The Nicaean Empire, like Byzantium of the Komnenoi and Angeloi of the twelfth century, went on to gain dominant influence over the Seljukid Sultanate of Rum in the 1250s. However,...