The Islamic Moors conquered most of Spain in 711 A.D. after the descendents of the Visigothic warriors that had conquered Roman Hispania in 415 A.D. had become a decadent and lazy ruling class with the passage of time.
The Christians made a stand in the mountain strongholds of Galicia and Asturias and defeated the Islamic Moors in 718 A.D. at Alcama thus turning the tide of Islamic conquest.
Thus began the Reconquista of Spain that lasted until Granada, the last Moorish kingdom in the Iberian Peninsula, was conquered in 1492.
The Reconquista was the earliest, the longest and the only completely succesful European Crusade in Christendom.
The Surrender of Moorish Granada, 1492
What about Russian lead liberation of Balkans and Russia itself? If West did not oppose it(Crimean War etc), probably Constantinople("Istambul") and coast of Asian Minor("Turkey") would be still Christian today.
Which was finalized by possibly the greatest woman in history (after Virgin Mary of course) - the Queen Isabella