No other faith is so much related to the political climate than the Uniates, currently centered around their church of Holy Trinity in the Old Town of Vilnius.
The Grand Duchy of Lithuania was ruled by the Catholic Lithuanian leaders but after the major expansions of 14th and 15th centuries (to modern-day Belarus and Ukraine) the majority of its population were Eastern Orthodox Slavs. There were many attempts to solve these divisions. Grand Duke Vytautas spend much time attempting to influence the contemporary religious leaders to solve the East-West schism of Christianity altogether.
This proved to be far-fetched and so the later Grand Dukes of Lithuania opted to solve the problem locally rather than globally by establishing the Uniate church in 1596 (Union of Brest). Its adherents were allowed to continue the Eastern Orthodox religious practices, but the frame of the church became Catholic, with the Roman Pope on top of hierarchy.
With the annexation of Lithuania by the Russian Empire in 1795 the state-sponsored role of the Uniate church ended almost overnight and its many churches and 95 monasteries were closed down or ceded to the Russian Orthodox church. Uniate church was also among the most persecuted ones during the Soviet occupation. The result is that the Uniate Christianity is now very weak. Most of its 350 adherents still are, as they always used to be, Eastern Slavs, primarilly Ukrainians.