Muhammad and his forces marched northwards to Tabuk, near the Gulf of Aqaba in October 630. It was his largest and last military expedition. After arriving at Tabuk and camping there, Muhammad's army prepared to face the Byzantine invasion. Muhammad spent twenty days at Tabuk, scouting the area, making alliances with local chiefs. With no sign of the Byzantine army, he decided to return to Medina. Though Muhammad did not encounter a Byzantine army at Tabuk, according to the Oxford Encyclopedia of the Islamic World, "this show of force demonstrated his intention to challenge the Byzantines for control of the northern part of the caravan route from Mecca to Syria".