The relationships between Rus and Lithuania in the times of Ivan III and Kazimierz (Casimir IV Jagiellon), son of Jogaila, were not peaceful. Lithuania tried to undermine the strengthening Muscovy by supporting Novgorod and Tver and incited the Mongols against Muscovy, but was not strong enough for the open warfare. After Vytautas, the complicated internal situation in Lithuania weakened the country. Many knyazes who did not support Polonization and the Catholic influence joined Muscovy (see chapter 41). Conflicts with Muscovy were too dangerous for Lithuania, but after the death of Casimir (1492), they became inevitable. Casimir's son, Jan I Olbracht (John I Albert of Poland) , became the king of Poland, and Lithuania elected his brother, Alexander Jagiellon, as the knyaz. Leveraging this disagreement between Poland and Lithuania, Ivan III started a war against Alexander, and Lithuania had to cede formally the lands of the knyazes who had already pledged allegiance to Ivan (Vyazemskies, Novosilskies, Odoyevskies, Vorotynskies, Belevskies) and recognized his title of "the Lord of all Rus". The peace was confirmed by the marriage of Alexander, son of Kazimierz, and Helen (Yelena), daughter of Ivan III.
Alexander was a Catholic, but he promised not to force his Orthodox wife to convert. However, he had to break his promise because of the pressure of his Catholic environment. The life of Yelena Ivanovna was sad and her father's demands that she should be treated better, were in vain. On the other hand, Alexander was also annoyed by Ivan accepting new knyazes who refused to stay in Catholic Lithuania. So, knyaz Belsky and knyazes of Novgorod-Seversky and Novgorod-Chernigovsky who possessed huge patrimonies along Dnieper and Desna rivers. The war between Muscovy and Lithuania finally becam inevitable. It started in 1500 and continued till 1503. Lithuania was supported by the Livonian Order and the Crimean khanate supported Rus. Muscovy was stronger than Lithuania and the Livonian Order and the truce signed in 1503 confirmed that the new lands belonged to Muscovy. The Livonian Order also lost. Earlier, Muscovy was slowly losing to the pressure from the West, but since Ivan III Muscovy fights back, returns some lands earlier conquered by the Livonian knights and even claims all Russian lands.
Waging wars with his Western neighbors, Ivan sought for allies in Europe. He sent ambassadors to Denmark, Hungary, Venice and Turkey. Strengthening Russian state was entering the European international stage.