Wittingly or not, a just-completed 10-day visit to Ukraine by Kirill I, the head of the Russian Orthodox Church, has exposed the dangers lurking in relations between Russia and Ukraine, the two most populous nations to emerge from the breakup of the Soviet Union.

It was Kirill’s first trip to Ukraine since he was elected patriarch in January. The visit opened on July 27 with an affirmation of Russian-Ukrainian brotherhood in Kiev, regarded as the cradle of Russian Orthodoxy. Prince Vladimir adopted Orthodoxy from Byzantium for himself and his subjects, who were baptized en masse in the Dnieper River in 988.

“If you will, Kiev is our common Jerusalem, from which our Orthodox faith came,” Kirill said after a service dedicated to the prince, St. Vladimir. “Praying here, we, the heirs of Vladimir’s baptism, living in different states, inviolately preserve the spiritual unity bestowed by him upon us.”

But if the call to unity was a constant theme, and Kirill even offered to take out Ukrainian citizenship, it was clouded both by demonstrators hostile to a visit they saw as an attempt to assert Russian domination, and by political, religious and military tensions that have festered and in some ways grown since the Soviet collapse in 1991.