Nationalism is an ideology whereby people believe that a leader can only be effective if he comes from the same ethnic group as the subject. On the other hand, ethnic cleansing is the elimination of a particular group of people based on their race, ethnicity or political affiliation. The ideology assumes that a leader who does not belong to a similar ethnic group as his subject is inappropriate. Nazism and the Balkan war are some examples of national cleansing that may have resulted directly from nationalism. Although nationalism is not directly related to ethnic cleansing, the two phenomenons occur simultaneously. This essay explores the two phenomenons with respect to post world war I Europe. Nationalism is believed to be the basis of ethnic cleansing although the reverse argument holds. Although the founders of nationalism had good intentions for European communities, the phenomenon ended up becoming a subject to misinterpretation. Nationalism developed from the needs of communities to protect their, military, industrial and geographical interests before it was narrowed down to ethnicity. This implies that ethnic cleansing was inevitable in a society that valued nationalism. Societies that valued nationalism could only maintain their values and interests by imposing ethnic cleansing.