Remember too, Greek Catholics, who are very much like the Russian Orthodox are loyal to the Vatican. The Russian Orthodox are not.
==Is Russia’s war on Ukraine about religion?
The history of Russian and Ukrainian Orthodoxy suggests the answer is complicated.==
On February 21, Vladimir Putin laid out his case to the Russian people for a war against Ukraine. In an hour-long, televised rant, the Russian president ridiculed the notion of Ukrainian statehood and independence. Modern Ukraine was invented by the Bolsheviks, Putin said, and should never have become independent of Russia after the collapse of the Soviet Union.
Putin put his tirade in religious as well as political terms. He argued that Russia and Ukraine share one culture and one Orthodox faith. Russian military action would correct the catastrophic historical mistakes that separated the two countries and their one religion. He argued that Ukrainian nationalists had taken possession of several Orthodox parishes that belong to the Moscow Patriarchate—and that Russia must defend its churches in Ukraine.
To understand what he meant, you have to go back to 988 CE. In what is now Crimea, Prince Vladimir (Volodymyr in Ukrainian) chose to be baptized into the official Christian faith of the Byzantine Empire. According to legend, Vladimir made this decision after his envoys to Constantinople visited Hagia Sophia and described for him the Orthodox liturgy, with its engagement of the physical senses and direction of them to God’s holy presence. “We no longer knew whether we were in heaven or on earth,” they exclaimed. When Vladimir returned to Kyiv, his warriors and their families were baptized en masse in the Dnieper River.
Both Ukrainians and Russians regard these events as birthing their respective nations. Vladimir’s Christianity unified disparate, rival tribes into one people. From that moment on, Orthodox Christianity would shape the art, architecture, music, literature, and thinking of the Eastern Slavs.
A sociopolitical ideal also emerged, one with deeply spiritual implications: a Holy Rus’, where all creation and human social relations would become transparent to divine beauty. This vision would be both threatened and renewed by historical developments. In the Middle Ages, Mongols swept across these lands, laying waste to Kyiv. When the princes of Muscovy threw off the Mongol yoke, Moscow emerged to replace Kyiv as the center of Slavic Orthodoxy, and those princes laid claim to the idea of Holy Rus’. The Islamic conquest of Constantinople in 1453 further strengthened Moscow’s conviction that it had inherited the mantle of defender of true Christianity. The mythology of Moscow as the Third Rome was born.
The Vladimir Mother of God—one of Russian Orthodoxy’s most beloved icons, now in Moscow’s Tretyakov Gallery—represents this journey of Orthodoxy into Russia. According to legend, the apostle Luke painted the icon. It came to Constantinople in the fifth century, to Kyiv in 1130, to Vladimir (northeast of Moscow) in 1155, and to Moscow in 1395.
So what about Kyiv? As history would have it, the Kyvian lands became borderlands under the domination of rival European powers: Austro-Hungarian, Polish-Lithuanian, and Russian. Ukrainian identity—and Ukrainian Christianity—absorbed influences from each.
In the western areas of Ukraine, under Polish Catholic influence, the Ukrainian Greek Catholic Church was dominant. Created in 1596, this church retains Orthodox forms of worship but aligns itself with the pope. When Stalin repressed resurgent Ukrainian nationalism after World War II, he liquidated this church. Some priests and parishes went underground; the majority were forced to become Russian Orthodox.
n central and eastern Ukraine, an autonomous Ukrainian Orthodox movement existed, and during the Bolshevik Revolution and the civil war that followed, an autocephalous Ukrainian Orthodox Church briefly established itself, only to be forced underground when the communists took control. (In Orthodoxy, autocephalous means that patriarchs are relatively autonomous and equal in power.)
With the dissolution of the Soviet Union in 1991, the religious picture in the now independent Ukraine became increasingly complicated. The autonomous Ukrainian Orthodox and Greek Catholic churches recovered legal status. Within the Russian Orthodox Church, a pro-Ukrainian faction declared its independence from the Moscow Patriarchate, but for years this group’s independence was not recognized by any of the world’s Orthodox churches. Meanwhile, Russia’s religious investment in the region was and remains high: a third of all Orthodox churches that are loyal to the Moscow Patriarchate lie within the territory of Ukraine. All of these churches see themselves as legitimate heirs of Holy Rus’.
More at: https://www.christiancentury.org/article/critical-essay/russia-s-war-ukraine-about-religion