Résumé : The present research is an analysis of the political decision-making process in Israel in relation to two crises, the summer of 1982 and the summer of 2006, preceding respectively the First and Second Lebanon wars. The present research is structured in accordance with the theoretical posture of Neoclassical Realism. Although still a young school of thought, the theoretical roots of Neoclassical Realism can be found in Classical Realism and Neo-realism - concerning the role of the State in the international system, and are integrated with the study of the domestic level and the role of the deciders in the elaboration of foreign policy decisions. By making the link between the international and domestic level explicit, this thesis allows grasping the full extent of the origins and implications of a State’s foreign policy. In addition, in order to study the relevance of a long-term approach in researches on decision-making processes, Historical Institutionalism complements Neoclassical Realism in the theoretical framework. To answer the research question the present research is based on the “process tracing” methodology, which aims at uncovering the mechanisms - that is the tangible expression of actors and their actions - and aims at explaining how these are linked to their surrounding environment.