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 Ottoman–Albanian Wars, 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:
We have been blocking this force (Turks) for almost seventeen years wasting our bodies, lives and all of our goods, and like the bastion and a bulwark of Christianity we daily defend Christian countries, as much as it is humanly possible. That is why we are telling you this: If we get defeated by the Turks, then they will be able to remove Christianity from Croats.
When Turks conquered Constantinople in 1453, Pope Callistus III urged all Christians to the Crusades. Many Croats, led by Saint John of Capistrano, were part of the army that defeated 150,000 Turks at the Siege of Belgrade in 1456. When Belgrade was conquered by the Turks in 1521 many Croatian writers and diplomats pointed out dramatic situation stating that Belgrade was the bastion of Christianity, the key to Europe and the fortress of the entire Kingdom of Hungary. In the following year German Parliament in Nuremberg called Croatia Zwingermaurer (Fortress) and the Austrian Archduke Ferdinand of Habsburg said that "chivalrous Christian nation of Croats is standing as a shield in front of Styria, Carinthia and Carniola, and the whole of Central Europe and Western Christendom." At the session, Prince Bernardin Frankopan asked for help, recalling that "Croatia is a shield and door of Christianity". Fran Krsto Frankopan stated on July 1, 1523 in the memorial to the Pope Adrian VI that Croatia is a "bulwark or door of Christianity, and especially bordering countries of Carinthia, Carniola, Istria, Friuli and Italy". Croatian baroque poet Vladislav Mencetić wrote in 1665:
Italy would have sunk into the deep waves from slavery if the Ottoman sea hasn't been streaking into the Croatian seashore.
In nearly 400-year-long war against the Ottoman Empire many Croatian warriors and heroes become known for their merits. Some of them are: 1. Marko Skoblić, Defender of Zemun who was tieded and thrown under an elephant because he refused to convert to Islam and to become loyal to the Ottoman Empire; 2. Petar Berislavić, Croatian ban who received blessed sword and a hat from the Pope Leo X in 1513 as a gift for the great victory at Hrvatska Dubica; 3. Petar Kružić, captain from Senj who was defending Fortress of Klis for 15 years; 4. Nikola Jurišić, Croatian nobleman who stopped 140,000 Suleiman's troops which were going to conquer Vienna; 5. Croatian Ban Nikola Šubić Zrinski who saved Pest with only 400 Croatian soldiers and in 1566 in the Siege of Szigetvár with 2.500 Croatian soldiers stopped Suleiman II's army with over 100,000 soldiers in their attempt to conquer Vienna and all of Europe; 6. Matko Talovac; 7. Ivan Lenković; 8. Marko Mesić; 9. Juraj V Zrinski; 10. Luka Ibrišimović
For its centuries-long stance against the Muslim advances, the Polish–Lithuanian Commonwealth also gained the name of Antemurale Christianitatis. In 1683 the Battle of Vienna marked a turning point in a 250-year-old struggle between the forces of Christian Europe and the Islamic Ottoman Empire. Wespazjan Kochowski in his Psalmodia polska (The Polish Psalmody, 1695) tells of the special role of Poland in the world (antemurale christianitatis – the bulwark of Christianity) and the superiority of the Polish political system (złota wolność – the golden liberty).