The coordinated September 11, 2001 attack on the United States resulted in a prolonged war on terrorism; which is still active today. Many people wonder how this could happen. Others want to know how to prevent this from happening again. Some wonder if world peace will ever be possible. The United States does not believe that peace will be possible until the threat of terrorism becomes obsolete. There is no clear answer to questions and concerns about terrorism, although there are several schools of thought on how to respond to terrorism. This paper will discuss; realism, liberalism and structuralism in an attempt to find a solution. I will offer foreign policy recommendations based on these theories; an examination regarding the application of these theories will show the advantages and disadvantages of each, as well as how the United States applies them to combat and eliminate terrorist threats today. Recommendations for applying realist theory include sending a strong message to nations hosting or supporting a known terrorist. This strong message should include an increase in military power, sanctions and, if necessary, a pre-emptive strike. Recent threats from our country, for example, the plot to blow up the White House, require a closer look at immigration. The Department of Homeland Security, therefore, should examine the records of immigrants who are in America, focusing on those whose visas have expired but remain in the states illegally. The benefits of following these recommendations are offensive, increased safety, and avoiding a potential repeat of 9/11. The core beliefs of realism support these recommendations because state security is the number one priority. Our military is the best in the world and is feared... middle of paper... for fighting terrorism. Realism is by far the preferred method in recent years. So far, the United States has avoided a repeat of 9/11, but it still has a long way to go to ensure security from terrorism in the 21st century. Works CitedDoyle, M. W. (2010). Liveralism and world politics. In MK Viotti Paolo, Theory of international relations (p. 159). New York: Longman. Galtung, J. (1982). A structural theory of imperialism. In V. John, Classics of International Relations (p. 266). New Jersey: Prentice Hall.JR, JS (n.d.). Hard and Soft Power in American Foreign Policy. Machiavelli, M. (n.d.). On Princes and the Security of their State.Viotti Paul, K. m. (2011). theory of international relations. New York: Longman.W., D.M. (2011). Kant, Living Heritage and Foreign Affairs. In R. J. Robert J. Art, International Politics (p. 115). Boston: Longmann.