John I Tzimiskes
With the beginning of the Byzantine offensives in the East and the Balkans in the 10th century, especially under the warrior-emperors Nikephoros II (r. 963–969), John I Tzimiskes (r. 969–976) and Basil II (r. 976–1025), newly gained territories were also incorporated into themes, although these were generally smaller than the original themes established in the 7th and 8th centuries.