This master's thesis deals with the issue of factors that influence the successfulness of insurgencies and the problem of determining the best course of action when fighting against insurgencies. The thesis will provide the theoretical basis neccesary for comprehending insurgencies and counterinsurgency operations, which will be followed by three case studies. The first will examine the American failure in the Vietnam War 1955-1975 which was caused by excessive reliance on military means in order to adress a political problem. The next study deals with the equally unsuccessful intervention in Afghanistan 2001-2021. The coalition forces were unable to defeat the Taliban movement because of their lack of understanding of the complex tribal relations in the country, their inability to destroy the Taliban bases in Pakistan and a lack of a common strategy between the government of Afghanistan and its foreign partners. The last case study deals with the Malaysian Emergency of 1948-1954, during which the British forces managed to defeat the insurgents by separating them from the population they depended upon. The case studies will then be compared using the operational factors of time, space and forces. Based on that comparison it can be concluded that success in counterinsurgency operations depends on the primacy of political means, the separation of insurgents and the population, and the curtailing of foreing aid being sent to the insurgent group.