In the past two decades, Radical Islam rooted in Europe became an obvious security threat. This monograph argues that Western Europeans are partially responsible for permitting or not preventing the presence of radical Islamists in the Balkans and therefore in EU. While Islam came in Western Europe with the wave of immigration from African and Asian Muslim countries in the 1970s and 1980s, Islam in the Balkans existed for centuries. Radical Islam in Europe was initially imported from the mujahedeens that came to fight in the Balkan wars in the 1990s, and only later boosted by the events of the post 9/11 world. To define a valid problem statement, this monograph offers understanding of the cultural differences between the Western European Muslims and the Balkan Muslims. While the Balkan Muslims that lived on European soil for centuries are among the most secular in the world, Western European Muslims that are recent immigrants are showing high level of intolerance and radicalism, opposing the democratic values embedded in Western European culture. The Western European states failed to integrate Muslims into their societies and declared the idea of multiculturalism as a failed project, at the same time asking the Balkans governments to accommodate Muslims, indirectly facilitating the infiltration of radical Islam. The purpose of this monograph is to evaluate the intensity of radical Islam in the Balkans compared with the same problem that Western Europe has, by explaining the connections between Balkans Islam and Western European Islam. The patterns show that radical Islamists' strategic objective is Western Europe, and not the Balkans itself. Balkan countries are merely a safe haven for radical Islam and base for further operations into Western Europe. The Muslim population in several Balkan states is vulnerable to the emergence of radical Islam that in the past two decades is targeting moderate Muslims using the social-economic instability in the Balkans and support from the global jihadist network. This monograph suggests that Western European countries must establish a joint and decisive strategic concept for preventing radicalization of its Muslim population, not excluding the Balkan countries as a significant factor for the overall European security.