On top of the 2014 seizure of Crimea and years of infiltration in eastern borderlands, Russia now poses a more severe threat to neighboring Ukraine.
Whether the nation faces a military invasion, or even a World War 2.5, or less bloody subversion and hoped-for domination, journalists these next few years will need to understand and depict the religious aspect of Ukraine's rising nationalism and resistance against Russian expansionism.
Here are some basics. Russia and Ukraine contain by far the two largest national populations in Eastern Orthodox Christianity. The new World Christian Encyclopedia edition (which belongs in every media and academic library) counts 114 million Orthodox in Russia for 79% of the population, and 32 million in Ukraine for 73%.
Terminology note for writers: "Eastern Orthodox" is the precise designation for such churches, related historically to the Ecumenical Patriarchate based in Turkey, that affirm the definition of Jesus Christ's divinity by the Council of Chalcedon (A.D. 451). The separate branch of so-called "Oriental Orthodox" is non-Chalcedonian; its largest national church is in Ethiopia.
Ukraine's ecclesiastical history, like its political history, is highly complex. The saga began with the A.D. 988 "baptism of Rus" in Kyiv (Russians prefer "Kiev") when Prince Vladimir proclaimed Orthodoxy the religion of his realm and urged the masses to join him in conversion and baptism.
Russians see Christendom's entry into Eastern Europe as the origin of their homeland and the Russian Orthodox Church. Russian President Vladimir Putin cites this history to support his claim for Ukraine as a client area within greater Russia instead of a validly independent nation. His post-Soviet Kremlin maintains close bonds with the Russian Church's Moscow Patriarchate, which in turn has centuries of ecclesiastical authority within Ukraine.