Abstract : The tectonic events of the past three years -- September 11 and Operation Enduring Freedom, the global war on terrorism, and the war in Iraq and its aftermath -- have dramatically affected the Muslim world and attitudes toward the United States. However, some of the dynamics that are influencing the environment in Muslim countries are also the product of trends that have been at work for many decades. The continuation of these trends will make management of the security environment in the Muslim world more difficult in years to come and could increase the demands on U.S. political and military resources. Consequently, it is important to develop a shaping strategy toward the Muslim world that will help to ameliorate the conditions that produce religious and political extremism and anti-U.S. attitudes. This RAND Corporation study has several purposes: (1) to develop a typology of ideological tendencies in the different regions of the Muslim world to identify the sectors with which the United States can find common ground to promote democracy and stability and counter the influence of extremist and violent groups; (2) to identify the factors that produce religious extremism and violence (i.e., the conditions, processes, and catalytic events that have given rise to Islamic radicalism); (3) to identify the key cleavages and fault lines among sectarian, ethnic, regional, and national lines and to assess how these cleavages generate challenges and opportunities for the United States; and (4) to identify possible strategies and sets of political and military options to help the United States meet challenges and exploit opportunities presented by changed conditions in the Muslim world. The regional structure of the report recognizes that while events since September 11 have affected U.S. relations with all parts of the Muslim world, they have done so in different ways in different regions. Abbreviations, glossary, and an extensive bibliography are included.