The surviving records on the internal history and rulers of the Emirate of Crete are very fragmentary. Following the studies of George C. Miles with the aid of numismatic evidence, he is tentatively identified as a son of the second emir, Shu'ayb, and the grandson of the conqueror of Crete and founder of the Emirate of Crete, Abu Hafs Umar. His reign is placed from c. 880 to c. 895. According to the Byzantine chronicler Genesios, sometime in the reign of the Byzantine emperor Leo VI the Wise (r. 886–912) he suffered a shipwreck off the coast of the Peloponnese, and was taken captive by the local governor, Constantine Tessarakontapechys.
He was apparently succeeded by his brother Muhammad ibn Shu'ayb al-Zarkun, but two of his sons, Yusuf and Ahmad, are held to have reigned later, in c. 910–915 and c. 925–940 respectively. According to a letter sent by the Patriarch of Constantinople, Nicholas I Mystikos, to Umar's son Yusuf, Umar had maintained a friendly correspondence with the Patriarch Photios.
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