Inspired by his successful campaign against Timur, Vytautas and Jogaila won support from Pope Boniface IX for organising a crusade against the Mongols. This political move also demonstrated that Lithuania had fully accepted Christianity and was defending the faith on its own, and that the Teutonic Knights had no further basis for attacks against Lithuania. The campaign resulted in a crushing defeat at the Battle of the Vorskla River in 1399. Over twenty princes, including two brothers of Jogaila, were killed, and Vytautas himself barely escaped alive. This came as a shock to the Grand Duchy of Lithuania and Poland. A number of territories revolted against Vytautas, and Smolensk was retaken by its hereditary ruler, George of Smolensk, and not re-conquered by Lithuanians until 1404. Vytautas waged a war in 1406–1408 against his son-in-law Vasili I of Moscow and Švitrigaila, a brother of Jogaila who with the support of the Teutonic Order had declared himself grand prince. A major stand-off between the two armies ended without a battle in the Treaty of Ugra, by which Velikiy Novgorod was granted to Jogaila's brother Lengvenis, and the important city of Pskov to Jogaila's envoy Jerzy Nos, the latter settlement a clear violation of the treaty of Raciąż. The war with Muscovy ended in December 1408, on terms that made further conflict with the Teutonic Order inevitable, despite Hermann II of Celje's attempt to negotiate a solution.