International responsibility of the state of nationality of the foreign fighters under the law of armed conflict

Every act against international law committed by a state entails the responsibility of that state. A state is deemed to have violated international law if it violates its international obligations by an act or omission, and if the behavior is attributable to the state. These principles are the most basic principles of international responsibility law and constitute the subject of our study. A state's violation of its international obligations is defined as an illegal act in international law and it is claimed that the state's responsibility arises from this act. The behavior of the state, which is considered to be unlawful, can occur as a result of an action or as a result of the state's inaction. If the state remains inactive where it should act and therefore violates an international obligation, the responsibility of the state in question will come to the fore. In order for the state to be held responsible for this obligation, the behavior must be attributable to the state. The phenomenon of foreign fighters, created by those who fight for different purposes in the armies of states where they are not citizens, continues with changing motivations today. The purpose of the wars remains the same, but it has turned into a situation that changes in form, duration, means and actors. Foreign fighters, who take more and more roles in armed conflict environments, have increased their activities in the post-Cold War period. In our study, the responsibility of the state of which the citizens of the people called mercenaries, private military company employees or foreign fighters in different periods of the war history are discussed. While aiming to raise awareness about foreign fighters who threaten international security day by day, the study focuses on the international responsibility of the state of citizenship for the illegal actions of foreign fighters within the scope of the law of armed conflict. Keywords: Law of armed conflict, international humanitarian law, international responsibility of the state, international illegal act, foreign fighters.