During Russian rule, Catholics, primarily Poles and Lithuanians, suffered great persecution not only because of their ethnic-national background, but also for religious reasons. Especially after the uprisings of 1831 and 1863, and within the process of Russification (understanding that there is a strong link between religion and nationality), the tsarist authorities were anxious to promote the conversion of these peoples to the official faith, intervening in public education in those regions (an Orthodox religious education was compulsory) and censoring the actions of the Catholic Church. In particular, attention was focused on the public actions of the Church, such as masses or funerals, because they could serve as the focus of protests against the occupation. Many priests were imprisoned or deported because of their activities in defense of their religion and ethnicity. In the late nineteenth century, however, there was a progressive relaxation of the control of Catholic institutions by the Russian authorities.