after a series of campaigns in the region of the River Euphrates and in the Tauros mountains, drove the Arabs from the eastern borders of the Empire and regained control of the trade routes in the East. Meanwhile, Arab pirates (called Saracens in the Byzantine sources) launched assaults from Crete, Egypt and other parts of Africa, plundering and sacking the coastal and insular regions of Byzantine Empire. The largest among these invasions was the siege of Thessalonike in 904, under the leadership of Leo of Tripoli. The city was savagely sacked and many of its citizens were murdered or sold as slaves. There is no need to mention the severe repercussions this had on the urban life and the economy of the areas stricken by these attacks.
The most important campaigns against the Arabs were those conducted by Romanos I Lekapenos in the East and in the Aegean region. The high points in his expeditions were the seizure of Melitene in 934, by his extremely capable general John Kourkouas, and of Edessa in 943, from where he took and transported to Constantinople the Holy Mandylion (Towel). The importance of these conquests lies not only in the territorial expansion of the Empire but also in the restoration of security for the rural population of Asia Minor that had suffered much from repeated invasions. At the same time, the defence of the borders was enforced by the so-called 'akritai' (border defenders), mentioned in the Byzantine military treatises of the 10th and 11th centuries.
The conflicts between the Arabs and Byzantines continued in the reign of Constantine VII Porphyrogennetos. A few successful Byzantine operations in Syria and Armenia in 947-8, were followed by their unsuccessful attempt to reoccupy Crete. The military operations continued in the following years with alternating victories for both sides.