Svatopluk's career started in the 860s, when he governed a principality within Moravia, the location of which is still a matter of debate among historians, under the suzerainty of his uncle, Rastislav. In 870 Svatopluk dethroned Rastislav, who was a vassal of Louis the German, and betrayed him to the Franks. Within a year, however, the Franks also imprisoned Svatopluk. After the Moravians rebelled against the Franks, Svatopluk was released and led the rebels to victory over the invaders. Although he was obliged to pay tribute to East Francia under the peace treaty concluded at Forchheim (Germany) in 874, he was able to expand his territories outside the Franks' sphere of interest in the following years. His forces even invaded the March of Pannonia within East Francia in 882.