Before the tenth century, Russians practised Slavic religion. As recalled by the "Primary Chronicle", Orthodox Christianity was made the state religion of Kievan Rus' in 987 by Vladimir the Great, who opted for it among other possible choices as it was the religion of the Byzantine Empire. Since then, religion, mysticism and statehood remained intertwined elements in Russia's identity. The Russian Orthodox Church, perceived as the glue consolidating the nation, accompanied the expansion of the Russian Empire in the eighteenth century. Czar Nicholas I's ideology, under which the empire reached its widest extent, proclaimed "Orthodoxy, autocracy and nation" ("Pravoslavie", "samoderzhavie", "narodnost"') as its foundations. The dominance of the Russian Orthodox Church was sealed by law, and, as the empire incorporated peoples of alternative creeds, religions were tied to ethnicities to skirt any issue of integration. Until 1905, only the Russian Orthodox Church could engage in missionary activity to convert non-Orthodox people, and apostasy was treated as an offense punishable by law. Catholicism, Islam and other religions were tolerated only among outsider ("inoroditsy") peoples but forbidden from spreading among Russians.