The basis of this doctoral work rests on the fact that the state terrorism is ignored in the context of mainstream security and terrorism knowledge. Security studies as well as rapidly growing terrorism studies are predominantly focused on non-state terrorism. Critical voices which indicating the importance of the state terrorism phenomenon have emerged in the mid-1990s. Based on the starting points of critically oriented security studies and terrorism studies, this work analyzes the methodological, epistemological and even ontological aspects of the phenomenon of state terrorism. It is argued that the state terrorism is systematically neglected area of knowledge, although it is very evident phenomenon. In the first part of this doctoral work the classical and the contemporary political, social, philosophical thought and jurisprudence important for the understanding of the state security, terrorism and state terrorism have been examined. Max Weber's concept of the state and difference between legitimate domination (Herrschaft) and coercive power (Macht) in the exercise of sovereign state functions is at the center of theoretical discussions. We claim that this distinction remained outside of much Western scholarship. Their concepts are based on logic of what the state and its relations to society should be not what it is. In contrast to this mainstream normative oriented model we examine the empirical reality which is laden of state terrorism examples. Therefore, the second part of this work is dedicated to analysis of existing knowledge about terrorism and state terrorism. The emphasis is on the definitions of terrorism, so for this purpose the database of 373 terrorism definitions was constructed. Definitions collected from the scientific and academic sources, the expert sources, the available official sources of various institutions and organizations, news, etc. were subjected to content and frequency analysis. Those analyses indicated six key elements used for defining state terrorism, which is relevant to the selection of empirical cases. It is found that the state terrorism is the use of organized force and violence or threat to use violence as a means of intentional spreading fear and terror based on the anticipated reactions of broader psychological effects which seeks to achieve political objectives and which is conducted and/or sponsored by the state. It is not an ideology, but the strategy and tactic that can be used by all, including the states. Despite the fact that the most of the definitios are actor-neutral and that their contents coincide, there is no unified definition. According to such understanding, the third part is a focused study with a lot of cases (N=21) where the unit of analysis was state terrorism and analytical sub-units were states (cases) selected from the one century time span (1914th-2014th) complemented with the most recent cases (until the end of 2016th). Thus, it is a diachronic analysis (cross-historical analysis). Since the selected cases differ in several relevant independent variables (social, economic, geographic, cultural) the comparative analysis is based on the most different systems research designs. The basic criterion of comparison was the regime (totalitarian, authoritarian and democratic) in accordance with the tipology of Juan Linz. The main aim of such typology and case selection was to test the general thesis: terrorism is an integral instrument of state action that occurs in all types of political regimes and which states used/use as a form of rational choice to achieve their goals. The third part includes political and sociological analysis of primary and secondary sources for each case (state). The analysis of state terrorism included Italy during Mussolini, Nazi Germany, Lenin and Stalin Russia/Soviet Union, communist Poland, Mao Zednog's China, North Korea regime and Idi Amin's Uganda as a totalitarian regimes. The second group of states are, according to Linz proposal, authoritarian regimes. Here is a Serbian example of state sponsored terrorism in Sarajevo 1914 and assassination of Archduke Franz Ferdinand. Another example is Yugoslavia from the mid of 1960 even if it is not purely clear is it predominantly totalitarian or authoritarian regime. Other examples are the rule of Francisco Franco in Spain, death squad in Argentina, Gaddafi's Libya, the rule of Shah Reza Pahlavi in Iran and Suadi Arabia sponsoring of terrorism. Within a democratic cluster the United States of America, Israel, United Kingdom, France, Russian Federation, modern Turkey and Macedonia were analysed. The main findings in turn suggest that the state terrorism was/is practiced in totalitarian, authoritarian and democratic systems, was/is used in war or peace, was/is used by the rich and the poor countries of different cultural, political, economic, geographic and other features. In other words, terrorism is an universal form of state action, but the specific context of each of the analyzed cases does not provide the right to generalize or compare countries according to the basic independent variables - the type of regime. Divided societies and various social cleavages like political (ideological), ethnic, cultural, language, religious, economic and other are evident in the most of the internal state terrorism cases. Although the contexts of countries are quite heterogeneous, in each case analyzed rationality is a common feature of state terrorism. Statet are trying to achieve political goals in the most effective way, what is decisively for using a specific form of violence or threats of violence that we call terrorism. Although it is one of the most frequently used terms in the social sciences, it is evident that terrorism is not conceptually cleared. It is deeply socially constructed concept which depends on a variety of interests. This also affects the contemporary counterterrorism policy. Within the science and policy, terrorism is predominantly viewed as a war and/or criminal. Terrorism is not treated as a phenomenon that is generated from the political area and counterterrorism policies do not target the real causes of terrorism. The perspective of terrorism as a war and crime which is imposed by politics that cooperates with science, leads to a spiral of violence. Illegal and immoral state counterterrorism actions lead to the even more brutal reactions of non-state groups. This trend is especially noticeable from September 9/11 when the "war on terror" started. From this moment it is especially evident that in the name of national security, the degradation of democratic values and endangering human rights and civil liberties have begun. This is best reflected in the new security policies, counterterrorism laws and the state of emergency institute. Also, the democratic deficits are obvious in the examples of interventions in other countries. Illegal character of the war in Iraq shows that international law is not a guarantee nor law nor justice. Those are some contemporary examples of state illegal actions which could be classified as state terrorism in democratic states, but the history is full of state terrorism evidence. Totalitarian and authoritarian regimes in the 20th century, as well as some actual examples, suggesting that the scientific community is biased and ignores the important historical facts as well as contemporary trends. By securitization of terrorism concept, the state harnessed science to its own interest – first of all creating counterterrorism policies. Instrumented science can act only within the limits defined by the state. The main characteristic of the joint state and scientific activity is hypocrisy where identical phenomena do not have identical names. State and science are taking a morally superior position, so state terrorist actions are called "necessary security measures", and terrorism as a pejorative term is reserved only for non-state actors. Further scientific and political ignoring of state terrorism topic, denying a unique definition of terrorism, refusing the recognition of state crimes that fall into the category of terrorism and insistence on counterterrorism as war strategy only feeds the modern evil of non-state terrorism. As long as there is not a change of paradigm in which the force will be firmly under the auspices of the law and policy of double standards will not exist, it is not realistic to expect that the state will eliminate the problem of contemporary non-state terrorism.