Oleg of Novgorod
Then, in 904 the renegade Leo of Tripolis sacked Thessalonica with his pirates—an event described in "The Capture of Thessalonica" by John Kaminiates—while a large-scale expedition to recover Crete under Himerios in 911–912 failed disastrously. Nevertheless, the same period also saw the establishment of the important frontier provinces ("kleisourai") of Lykandos and Leontokome on territory recently taken from the Arabs. In 907 Constantinople was attacked by the Kievan Rus' under Oleg of Novgorod, who was seeking favourable trading rights with the empire. Leo paid them off, but they attacked again in 911, and a trade treaty was finally signed.