National security and sustainability are the main priority of any state. Therefore the Republic of Lithuania as well as any other state follows its National Security Strategy which establishes the interests of national security, directions of its evolution, the security and defence policy in general, means and types of risk factors and threats to the national security. This study investigates the issues of legal preparation in the military high school. The topical issues directly related to the national defence and security which arise in the run of the training course for the military, especially junior leaders at the institution of higher education in the sphere of providing them with the basic legal knowledge, are presented and examined in the article. In the process of training and upbringing of a junior leader more attention is paid to their professional skills and competencies, and a leader’s and subordinate’s personality, therefore, a system of legal preparation and training provided for students of this kind of educational institutions, its role and degree of influence on personal qualities of a future leader have not yet been studied and described in scientific publications. The above mentioned observations determined the rationale for choosing the topic for the research paper. Its relevance is without doubt. It has been concluded that a leader who is politically correct and competent in the legal sphere can ensure that the decisions made are well-reasoned, consistent and adequate, and they are aimed at the elimination of possible disagreements which might emerge in the sphere of human resource management, management of military units in the run of resolving their daily tasks, holding negotiations at any levels, as well as enhancement of the army’s defensive power in general.