Analysis of information sources in references of the Wikipedia article "Siege of Kazan" in English language version.
Finally, the Russians, under Ivan the Terrible, defeated the Tatars in 1552 and firmly established Russian rule. In celebration of this conquest, the czar built two churches in the Moscow Kremlin and on the spires of the Church installed the Orthodox Cross over an upside down crescent, the symbol of Islam.
Sometimes the bottoms of the Crosses found on Russian churches will be adorned with a crescent. In 1486, Tsar Ivan IV (the Terrible) conquered the city of Kazan which had been under the rule of Moslem Tatars, and in remembrance of this, he decreed that from henceforth the Islamic crescent be placed at the bottom of the Crosses to signify the victory of the Cross (Christianity) over the Crescent (Islam).
It would be convenient to characterize the relationship between Russia and Islam by its history of conquest and tension. After all, the emblem of the Orthodox Church is a cross on top on a crescent. It is said that this symbol was devised by Ivan the Terrible, after the conquest of the city of Kazan, as a symbol of the victory of Christianity over Islam through his soldiers.
