In 833, Emperor Theophilus sent the nobleman Petronas Kamateros, who had recently overseen the construction of the Khazar fortress of Sarkel, to take direct control over the city and its environs, establishing the theme of Klimata/Cherson. It remained in Byzantine hands until the 980s, when it reportedly fell to Kiev. Vladimir the Great agreed to evacuate the fortress only if Basil II's sister Anna Porphyrogeneta would be given him in marriage. The demand caused a scandal in Constantinople. As a pre-condition for the marriage settlement, Vladimir was baptized here in 988, thus paving the way to the Baptism of Kievan Rus'. Thereafter Korsun' was evacuated.