Leo secured the Empire's frontiers by inviting Slavic settlers into the depopulated districts and by restoring the army to efficiency; when the Umayyad Caliphate renewed its invasions in 726 and 739, as part of the campaigns of Hisham ibn Abd al-Malik, the Arab forces were decisively beaten, particularly at Akroinon in 740. His military efforts were supplemented by his alliances with the Khazars and the Georgians.