After inheriting the Galician throne upon the death of Daniel in 1264, Leo moved the principality's
capital from
Halych to the newly founded city of
Lviv, which had been named after him by his father. Unlike his predecessor, who pursued a western political course, Leo worked closely with the
Mongols and together with them invaded Poland. However, although his troops plundered territory as far west as
Racibórz in
Silesia, sending many captives and much booty back to Galicia, Leo did not ultimately gain much Polish territory. He cultivated a particularly close alliance with the Tatar
Nogai Khan. He also attempted, unsuccessfully, to establish his family's rule over
Lithuania. Soon after his younger brother
Shvarn ascended to the Lithuanian throne in 1267, Leo organized the murder of
Grand Duke of Lithuania Vaišvilkas. Following Shvarn's loss of the throne in 1269, Leo entered into conflict with Lithuania. In 1271-1272 he took part in the Polish succession war on the side of Bolesław the Chaste together with his brother Mstislav, Prince of
Lutsk, and later joined his cousin
Volodymyr Vasylkovych in a campaign against the Jotvingians, which ended with the latter suing for peace. In 1274–1276, Leo fought a war against the new Lithuanian ruler —
Traidenis — but was defeated. Lithuania annexed the territory of
Black Ruthenia with its city of
Navahrudak. In 1279, Leo allied himself with King
Wenceslaus II of Bohemia and invaded Poland. His attempt to capture
Kraków in 1280 ended in failure. That same year, however, Leo defeated the
Kingdom of Hungary and temporarily annexed part of
Carpathian Ruthenia, including the town of
Mukachevo. However, other historians have pointed out that no contemporary documentary evidence supports such an annexation, and that Hungarian royal charters consistently list
Munkács and surrounding fortresses as part of the Kingdom of Hungary. Nevertheless, at least one known document issued by Gregorius,
Count of Bereg, dated with 1299, mentions him as a
vassal of "Leo, Duke of Ruthenians". It is likely that most of Carpathian Ruthenia returned under Hungarian rule after Leo's death, as another document issued by Gregorius in 1307 contains no mentions of Galician princes. The last Galician garrison in the region lost its castle to Hungarians in 1322. In 1285 Leo allied himself with the Lithuanians against the Polish duke Bolesław, who was plundering his principality. However, he refused to personally join the Lithuanian troops and prevented his son Yuri from taking part in the campaign, fearing
revenge for the murder of Vaišvilkas. In 1287 Leo joined the
Golden Horde khan Talabuga in his
campaign against Poland, which led to great devastation in
Volodymyr and its vicinity. In 1289 he personally visited his ally Wenceslaus in
Opava and returned to Lviv with lavish gifts, as well as rich booty captured from the Poles. At the time of Leo's death in 1301, the state of Galicia-Volhynia was at the height of its power. ==Legacy==