Islam was first introduced to Croatia by the Ottoman Empire during the Croatian–Ottoman Wars that lasted from 15th to 16th century. During this period some parts of the Croatian Kingdom were occupied which resulted in numerous Croats converting to Islam, some after being taken prisoners of war, some through the devşirme system. Nonetheless, Croats strongly fought against the Turks during these few centuries which resulted in the fact that the westernmost border of the Ottoman Empire in Europe became entrenched on the Croatian soil. In 1519, Croatia was called the "Antemurale Christianitatis" by Pope Leo X.