Some of the Khazar prisoners were drowned on al-Jarrah's orders. His army reduced the neighbouring fortresses as well, and continued their march north. The strongly garrisoned fortress of Wabandar capitulated in exchange for tribute, but the Arab advance was cut short before reaching the next important Khazar settlement, Samandar. Despite their success, the Arabs had not yet defeated the main Khazar army, which like all nomad forces was not dependent on cities for supplies. The presence of this force near Samandar, as well as reports of rebellions among the mountain tribes in his rear, forced the Arabs to retreat to Warthan south of the Caucasus. On his return, al-Jarrah reported on his campaign to the Caliph, but requested additional troops to defeat the Khazars, an indication of both the severity of the fighting and perhaps, according to Blankinship, that his campaign was not such a resounding success as portrayed in the Muslim sources.