Antemurale Christianitatis

Antemurale Christianitatis (English: Bulwark of Christianity) was a label used for a country defending the frontiers of Christian Europe from the Ottoman Empire.

In the 15th century Pope Pius II, admiring , waged mainly by Skanderbeg defined Albania as Italy's bastion of Christianity Latin: Antemurale Christianitatis Italiaeque. The pope himself declared the war to the Ottoman Empire in 1463, but such war was never fought, as the following year he died at Ancona, while still organizing the naval attack on the Ottomans.

Pope Leo X called Croatia the Antemurale Christianitatis (Croatian: Predziđe kršćanstva) in 1519 in a letter to the Croatian ban Petar Berislavić, given that Croatian soldiers made significant contributions in war against the Ottoman Empire. The advancement of the Ottoman Empire in Europe was stopped in 1593 on Croatian soil (Battle of Sisak), which could be in this sense regarded as a historical gate of European civilization. Nevertheless, the Muslim Ottoman Empire occupied part of Croatia from the 15th to the 19th centuries, and a large number of Croats converted to Islam. However, Pope Leo X wasn't the first that gave Croatia such a title. The nobility of the southern Croatian regions sent a letter to Pope Alexander VI and Roman-German emperor Maximilian I. on April 10, 1494 seeking help against the Ottoman attacks. In that letter Croatia was for the first time called bastion and a bulwark of Christianity:

...
Wikipedia