Jani Beg abandoned his father's Balkan ambitions and backed Moscow against Lithuania and Poland. Jani Beg sponsored joint Mongol-Rus' military expeditions against Lithuania and Poland. In 1344 his army marched against Poland with auxiliaries from Galicia–Volhynia, as Volhynia was part of Lithuania. In 1349, however, Galicia–Volhynia was occupied by a Polish-Hungarian force, and the Kingdom of Galicia–Volhynia was finally conquered and incorporated into Poland. This act put an end to the relationship of vassalage between the Galicia–Volhynia Rus' and the Golden Horde. In 1352, a Mongol-Russian army ravaged Polish territory and Lublin. The Polish King, Casimir III the Great, submitted to the Horde in 1357 and paid tribute in order to avoid more conflicts. The seven Mongol princes were sent by Jani Beg to assist Poland.