9/11 and subsequent islamist attacks against western, particularly American, targets have profoundly affected the international climate. This articles deals with two questions: (1) what is the nature of the islamist challenge? (2) which answers have been formulated by the west? It concludes with some tentative suggestions. Islamic fundamentalism or Islamism is defined as an antidemocratic and anti-pluralistic political project with a specific societal countermodel derived from an interpretation of Islam, yet clearly different from it. In fact, islamism has more in common with other fundamentalisms than with Islam. The USA is today at the center of a debate with global consequences, exacerbated by the mutual vulnerability between societies caused by globalization. Arguing against voices tending to relativize islamism's significance and scope, we point at the danger posed by means of violence viz. weapons of mass destruction in the hands of unappeasable groups. Those who accept islamism as an ally by virtue of its 'anti-imperialism' neglect the fact that its profoundly antirationalist philosophy and reactionary program stands closer to fascism than to the left. It is important to clarify that terrorism is just one of the means employed by islamist groups, and that a "war against terrorism" such as advocated by the Bush administration is therefore besides the point. However, while only a minority of islamist groups is violent, all of them are antiwestern: the threat must be taken seriously. Post-9/11 western reactions to the islamist phenomenon are here primarily gauged from the perspective of the US. They provoked a comprehensive rethinking of its foreign policy, from realistic-containment to aggressively idealistic-oriented. This reformulation is analyzed as outcome of the interaction between six positions: (1) the anti-imperialist and sometimes islamophile New Left (both Marxist and post-modernist), (2) the anti-totalitarian democratic Old Left, (3) status quo oriented neorealism, (4) culturalists, (5) the traditional and mostly islamophobic Right, an assortment of old-style conservatives, fundamentalist Christians, and isolationists, and (6) neoconservatives, many of Leftist origin, who militate in favor of exporting "American values" (often undistinguishable from secular democratic modernity as such) across the world in general - and to the Islamic world in particular - as a precondition for US security. After 9/11 the anti-interventionist positions shared (for different reasons) by the Far Left and the traditional Right lost credibility, while the traditional state-centered power politics of neorealists, who had long stood at the helm of US foreign policy, proved unable to come to grips with the islamist phenomenon. It seems that a coalition of interventionist old Leftists and neoconservatives closed the ideological hiatus and provided the justifications for newly interventionist US policies (e.g. in Afghanistan and Iraq). However, the results of these interventions have not so far confirmed the interventionists' predictions. The last part of the article assesses the moral dilemmas of both interventionist and anti-interventionist positions, arguing that while interventions may under certain circumstances be justified - e.g. in self-defense; or when a regime is threatening world peace; or to liberate a "captive" nation oppressed by a non-representative dictatorship - and repression may be inevitable, it provides no cure. There exists no long-term military solution to the challenge of violent Islamism, which can only be treated by addressing its social and political origins. These roots must be sought in mass alienation and social dislocation caused by globalization, which render significant parts of the Islamic world vulnerable to the islamist temptation. An adequate response will have to incorporate elements of distributive justice, empowerment of the Islamic world, and a values renewal in the west.