But this common heritage has also become a point of contention. Russians call the prince of Rus' Vladimir; for Ukrainians, he is Volodymyr. He was baptized in Crimea, what is now disputed territory between Russia and Ukraine. When Vladimir/Volodymyr returned to Kiev (or Kyiv), he had his warriors baptized en masse in the Dniepr River. In 1852, the Russian Empire commemorated the event by placing a 14-foot statue of Volodymyr above the riverbank. It soon became a symbol of the city. Not to be outdone, President Putin unveiled a 52-foot statue of Prince Vladimir near the Kremlin in Moscow in 2016.

Ukrainian identity is complicated by regional differences. What is now western Ukraine was at various times under the influence of the Polish-Lithuanian and Austro-Hungarian empires, whereas eastern Ukraine was more thoroughly Russified. Other areas of the country were influenced by Romania and Greece. Most Ukrainians today speak both Ukrainian and Russian, but they speak Ukrainian with different accents and vocabularies.

This complex history has also shaped Ukraine's religious life. At the end of the sixteenth century, a Ukrainian Greek Catholic Church emerged; its churches were allowed to retain the Orthodox liturgy and calendar in exchange for pledging allegiance to the pope. With the rise of the Russian Empire in the eighteenth century, the Russian Orthodox Church became dominant in central and eastern Ukraine.

The picture became more complicated in the twentieth century. After the 1917 Bolshevik Revolution, civil war broke out, and Ukraine was briefly independent. With the encouragement of the Ecumenical Patriarch in Istanbul, a body that called itself the Ukrainian Autocephalous Orthodox Church emerged, although other Orthodox churches did not formally recognize it. When the communists consolidated power in Ukraine, this church went underground. The Russian Orthodox Church continued to exist in Ukraine, but as in Russia most of its monasteries and parishes were closed, and thousands of its faithful were martyred. In 1944--45, Stalin liquidated the Ukrainian Greek Catholic Church; those who did not flee into the catacombs were forced into what remained of the Russian Orthodox Church.

With the collapse of the Soviet Union and the birth of an independent Ukrainian state in 1991, the Ukrainian Autocephalous Orthodox Church and the Ukrainian Greek Catholic Church recovered legal status, and the Russian Orthodox Church gave a large measure of autonomy to its branch in Ukraine, which is now known as the Ukrainian Orthodox Church of the Moscow Patriarchate (UOC-MP). At the same time, another complication arose: When he failed to be elected patriarch of the Russian Orthodox Church, the Ukrainian Metropolitan Filaret (Denysenko) proclaimed himself patriarch in Kyiv of yet another Orthodox Church, distinct from both the UOC-MP and the Ukrainian Autocephalous Orthodox Church.

The plot thickened with the Maidan Revolution in 2014, when Viktor Yanukovych, the pro-Russian president of Ukraine, fled the country. The new president, Petro Poroshenko, called for a new, independent Ukrainian Orthodox Church under the jurisdiction of the Kyiv Patriarchate--rather than under the Moscow Patriarchate--in order to help unite the country against Russian aggression. The U.S. State Department added tacit support.

In 2019, Ecumenical Patriarch Bartholomew issued a tomos of autocephaly to this church, now known as the Ukrainian Orthodox Church of the Kyiv Patriarchate (UOC-KP); the Ukrainian Autocephalous Orthodox Church merged with this new church. However, the status of the UOC-KP remains disputed among the other world Orthodox churches. Filaret still claims to be its patriarch, but the church is formally headed by Metropolitan Epiphanius of Kyiv. The Moscow Patriarchate rejects his legitimacy.

So today, three churches in Ukraine--the UOC-KP, the UOC-MP, and the Greek Catholic Church--and the Moscow-based Russian Orthodox Church regard themselves as the legitimate heirs of Prince Vladimir and his vision of a Holy Rus'. The Greek Catholics have drawn on Catholic social teaching to call for the rule of law and democratic political structures. The UOC-KP has found its identity in Ukrainian nationalism; even before the Russian invasion, it was collecting money for the Ukrainian army and blessing its campaign against pro-Russian separatists in the breakaway regions of Donetsk and Lugansk. Metropolitan Onufry (himself a Ukrainian) of the UOC-MP has tried to position his church as Ukrainian, though loyal to Patriarch Kirill in Moscow. Some of his priests have blessed the Russian-backed separatists in the east. Not all Ukrainian Orthodox believers pay attention to which jurisdiction their parish belongs to, although the ongoing tensions with Russia have led thousands of them to abandon the UOC-MP, or "Moscow Church."

After the Maidan Revolution, Patriarch Kirill became mostly silent about Ukrainian politics. Ever since Russia invaded Ukraine, he has issued only general calls for peace. But his tone in a sermon on February 27 grew darker. "God forbid," he declared, "that those evil forces that have always fought against the unity of Rus' and the Russian Church prevail." His words made clear that he sees an independent Ukraine as a threat to his vision of a Holy Rus' that unites Russians and Ukrainians.

Metropolitan Onufry has taken a different position. On February 24, he released a statement (which has not been posted on the Moscow Patriarchate website): "To our deepest regret, Russia has initiated armed force against Ukraine. . . . Insisting on the sovereignty and integrity of Ukraine, we appeal to President Putin to immediately cease this fratricidal war." Some UOC-MP churches have ceased commemorating Patriarch Kirill in the prayers of the Divine Liturgy.

The war in Ukraine is also a battle between conflicting visions of Holy Rus', Prince Vladimir's legacy, and the Orthodoxy that Russia and Ukraine share. The conflict will have serious consequences for Orthodoxy in Ukraine. If Putin prevails, the autocephalous UOC-KP could be outlawed. Kirill will likely not protest. What will happen to Onufry or other UOC-MP bishops in Ukraine? Will they leave the Moscow Patriarchate? Tragically, different Orthodox leaders, including Patriarch Filaret of the UOC-KP and Patriarch Kirill in Moscow, have hijacked Orthodoxy's vision of Holy Rus' for narrow nationalistic ends. In a truly Holy Rus', Russians would treasure what is precious in Ukraine's distinctive historical identity, and Ukrainians would affirm their special bonds with Russia.

John P. Burgess is James Henry Snowden Professor of Systematic Theology at Pittsburgh Theological Seminary.