The Cumans, a Turkic tribe approached the Danube Delta shortly after 1064-1065, and from 1068 the entire territory between the Aral Sea and the lower Danube were controlled by them. But this vast territory was never politically united by a strong central power. The different Cuman groups were under independent rulers or khans who meddled in the political life of the surrounding areas, such as the Rus' principalities and the Byzantine Empire. In attacking the Byzantine Empire, the Cumans were also assisted by the Vlachs living in the Balkan Mountains (now in Bulgaria) who showed them the mountain paths where no imperial guard was set up.