Until the collapse of the communist governments in 1989 Islamic radicalism was not a problem in the Balkans. But during the 1990s the situation changed, mainly because of Saudi financial support for the beleaguered Moslem minority in what used to be former Yugoslavia. This was most noticeable in Bosnia, where about half the population (of 4.6 million) were Moslem. During the 1990s Bosnia had some 4,000 Islamic radicals move in to help defend the local Moslems. The Bosnian Moslems were fighting a civil war against local Serb and Croat Christians. Any help was appreciated. Many of these foreign Moslems married local women and settled down. But some remained involved in Islamic radicalism, while others got involved in criminal activities. Some did both. Saudi Arabia contributed by sending Islamic radical preachers, and money for new Mosques and Islamic schools. Saudi Arabia has been doing this worldwide since the 1970s and has been reluctant to give it up. That's because it gives the Saudis a good way to get rid of many Islamic radicals. Otherwise these hotheads would have to be jailed or killed in Saudi Arabia, which would just turn them into martyrs for other Islamic radicals.
Most Bosnians tried to be tolerant about this growing Islamic radicalism in their midst, but after 2000 the Islamic radicals were getting aggressive and physical and the Bosnian hospitality was not having the desired effect. In 2007 Bosnia revoked the citizenship of 620 foreign Moslems and deported them. This was denounced by Islamic radicals at home and abroad. But threats of Islamic violence against the Bosnian government have come to nothing and Bosnia continues to be hostile to Islamic terrorism.
Then came ISIL (Islamic State in Iraq and the Levant) and since mid-2014 over a thousand Balkan Moslems, mainly from Albania, Kosovo and Bosnia, left to join ISIL and several hundred died in Syria. Those who returned were watched carefully and some of the most militant Islamic clerics were prosecuted for their support of ISIL and for aiding in recruiting. Bosnia, Albania and Kosovo did not become bases for Islamic terrorists but the decades of Saudi financed missionary work for the Saudi brand of Islam (which gave rise to al Qaeda and ISIL) led to the establishment of a growing minority of Bosnians who are Islamic conservatives and, at the very least, sympathetic to Islamic terrorism. Bosnia knows, better than most other Europeans that this will not end well.