During the late 9th and early 10th centuries, Simeon I achieved a string of victories over the Byzantines. Thereafter, he was recognized with the title of Emperor, and proceeded to expand the state to its greatest extent. After the annihilation of the Byzantine army in the Battle of Anchialus in 917, the Bulgarians laid siege to Constantinople in 923 and 924. The Byzantines eventually recovered, and in 1014, under Basil II "the Bulgar Slayer", a crushing defeat was inflicted on the Bulgarians at the Battle of Kleidion. By 1018, the last Bulgarian strongholds had surrendered to the Byzantine Empire, and the First Bulgarian Empire had ceased to exist. It was succeeded by the Second Bulgarian Empire in 1185.