In the early years of his rule, Leszek's policy focused mainly in
Kievan Rus'. In 1199 he helped Prince Roman of Vladimir-in-Volhynia with troops to reconquer the
Principality of Galicia, probably in gratitude for Roman's assistance against Mieszko III at Mozgawa in 1195. This alliance ended unexpectedly in 1205, however, when Roman decided to support Władysław III Spindleshanks' effort to recover the Seniorate Province (which supports the theory that Władysław III was expelled in 1202). Roman then invaded the domains of Leszek and Konrad for unknown reasons (although historians believe that this was due to the intrigues of Władysław III), venturing deep into their territory. Both forces clashed in the
Battle of Zawichost (14 October 1205), where Roman was defeated and killed. Leszek and Konrad then became involved in the conflict associated with the succession of Roman's domains, which was further complicated by the intervention of King
Andrew II of Hungary, who supported the rights of Roman's widow and children. Leszek and his brother initially led a coalition of Rurikid princes who wanted to remove Roman's children from Vladimir-in-Volhynia and Galicia. However, after some time, and in order to avoid a war with Hungary, they decided to sign a treaty. In 1206, Leszek met with Andrew II in
Volhynia, and afterwards the influence of the Hungarian rulers over Vladimir-in-Volhynia and Galicia was exclusive. Despite the agreement with the Hungarian King, the conflict continued. Shortly after, Roman's widow and her younger son
Vasilko, displeased with the Hungarian rule, decided to escape to Poland, where they found refuge at Leszek's court; her eldest,
Daniel had already been sent to the court of Andrew II. During their exile in Poland, they received the land of
Belz. A further confirmation of an active policy in Kievan Rus' was the marriages of Leszek and Konrad with Rurikid princesses. Leszek first married a daughter (name unknown) of
Ingvar Yaroslavich, Prince of Lutsk, and then
Grzymisława, perhaps a daughter of Yaroslav III Vladimirovich, Prince of Novgorod. Meanwhile, Konrad married
Agafia, daughter of
Svyatoslav III Igorevich,
Prince of Peremyshl. In 1210, Andrew II decided to replace the reigning prince of Vladimir-in-Volhynia with Roman's eldest son, Daniel. However, not wanting to lose his political influence, he decided to send his troops there. The expected Polish-Hungarian confrontation did not occur in the end, because Leszek was forced to have his army return after Mieszko Tanglefoot captured Kraków. Once the situation in the Seniorate Province was pacified, Leszek returned to Vladimir-in-Volhynia and Galicia in 1212. As a result of his military actions, he took several border towns. However, in 1213, he failed to prevent the capture of Galicia by the Hungarian boyar Władysław. Although a year later, he was defeated at the Bobrka river, the danger of the zone forced the Hungarian troops to retreat. In the same year, wanting to break the difficult relations with Hungary, Leszek, under the pressure of the Kraków aristocracy gathered around the voivode Pakosław, decided to conclude a peace treaty at
Spiš. According to this treaty, the government of Galicia–Volhynia was given to Andrew II's second son
Coloman, who was to marry Leszek's oldest daughter
Salomea. This treaty also gave Leszek territorial acquisitions in Kievan Rus' (the districts of
Przemyśl and
Lubaczów). Unfortunately, this alliance with Hungary did not last, because before the end of the year, Leszek decided to support the restoration of Daniel Romanovich in Galicia when it was clear that the local nobility did not accept the rule of Prince Coloman. The ambiguous policy of the Duke of Kraków cost him in 1215 when the Hungarians, impatient with the lack of help in securing the rule of Coloman, broke the alliance. Once the situation in Kievan Rus' seemed to be calm, the Hungarians sent an army against Leszek, using his support of Daniel as the rationale. During this campaign, Leszek lost the lands of Przemyśl and Lubaczów. After this defeat, Leszek wanted to make an alliance with
Mstislav Mstislavich, Prince of Novgorod. This new political approach failed to bring Leszek any positive results, because it prompted an alliance between Daniel Romanovich and Mstislav against him. As a result, the Duke of Kraków lost a small area between the
Narew and
Bug rivers in 1218. These successive failures forced Leszek to reconsider his previous alliance with Andrew II of Hungary. This time, the treaty between them was sealed with the formal marriage between their children, Coloman and Salomea. In return for his resignation over Galicia, Leszek received Volhynia in compensation, after Prince Daniel was expelled. The expedition under the command of Andrew II and Leszek was finally organized at the end of 1219. The combination of the Polish-Hungarian forces was a success, as Coloman and Salomea were formally proclaimed rulers of Galicia. In that year, Leszek also organized an unsuccessful expedition to Vladimir-in-Volhynia. Another expedition in 1221, this time with the help of Hungary, also ended in failure. Moreover, these invasions prompted Daniel, recently reconciled with Mstislav of Novgorod, to make a retaliatory expedition that ended with the imprisonment of Coloman and Salomea and the proclamation of Mstislav as Prince of Galicia. However, in 1223, an unexpected alliance developed between Mstislav and Andrew II regarding the succession of Galicia. It was agreed that after Mstislav's death, Galicia would be inherited by Andrew II's youngest son
Andrew. This caused a further change in the political situation, as Leszek and Daniel allied against them. Mstislav conducted an expedition against Leszek in 1225 with the help of the Cuman khan
Köten. This war, just like the previous ones, ended without a clear outcome despite temporary successes. Moreover, it resulted in another change of alliances in 1227 when Leszek joined with Hungary against Daniel. This was to be Leszek's last intervention in the long-running conflict with Kievan Rus'. == Conflict with Władysław III Spindleshanks ==