prisoner to Baghdad. In 906, al-Muktafi married a daughter of the second Tulunid ruler, Khumarawayh. She was probably a half-sister of the famous Qatr al-Nada, another daughter of Khumarawayh who was intended for him but ended up being married to his father in 893. Byzantine front Al-Muktafi also kept up the perennial conflict with the Byzantine Empire, with varying success. In May 902, al-Qasim ibn Sima al-Farghani was appointed to command of the frontier districts of the Jazira. In 902 or 903, a naval raid reached the island of Lemnos, dangerously close to the Byzantine capital, Constantinople; the island was plundered and its inhabitants carried off into slavery. Nevertheless, in May 903, the newly appointed governor of Tarsus, Abu'l-Asha'ir Ahmad ibn Nasr, was dispatched to the frontier districts with gifts for the Byzantine ruler, Leo VI the Wise (), and in return, Byzantine envoys arrived in Baghdad for negotiations on a prisoner exchange. The exchange eventually took place in September–October 905, at the river Lamus in Cilicia, but was interrupted because the Byzantines reneged on the agreed terms. After further negotiations, the exchange was completed in August 908. In the summer of 904, a Byzantine renegade in Abbasid service, Leo of Tripoli, led a major naval expedition of 54 vessels from the Syrian and Egyptian fleets, whose initial target reportedly was Constantinople itself. The Arab fleet penetrated the Dardanelles and sacked Abydos, as the Byzantine navy under the droungarios Eustathios Argyros was reluctant to confront them. Emperor Leo replaced Argyros with the more energetic Himerios, but Leo of Tripoli forestalled the Byzantines, turning back west and heading for the Empire's second city, Thessalonica, which he sacked after a three-day siege on 31 July 904. The sack of the city brought the Muslim fleet enormous booty and many captives who were taken to be sold as slaves, including the eyewitness John Kaminiates, who wrote the main account of the city's siege and fall. On land, however, the Byzantines held the upper hand: al-Tabari reports that in spring/early summer 904, a major Byzantine army, "ten crosses with one hundred thousand men", had invaded the borderlands and plundered as far as Hadath. In November, possibly as a retaliation for the sack of Thessalonica, the Byzantine general Andronikos Doukas invaded Arab territory, and won a major victory over the forces of Tarsus and al-Massisah (Mopsuestia) at Marash (Germanikeia). Further successes followed for both sides.