Ludwig Hagemann, a professor at the Faculty of Theology at Munster University who is a specialist in Islamic-Christian relations, presents in his book “Christianity against Islam” what he believes has been a two-hundred-year attempt to understand and deal with Islam, and to solve the unsolved problems between Christian Europe and the Islamic world. In his book, the author mentions the European attempts to counter the Islamic challenge: Islamic encroachment toward Christian Europe after the fall of Sicily, Spain and Portugal.