Defensive Operation
Defensive operation - a form of conducting combat operations by operational units of the armed forces; a set of agreed and interconnected battles, battles, and strikes conducted in a theater of war or a strategic direction according to a single design and plan with the aim of covering individual strategic or operational directions, areas, and objects, disrupting the enemy's offensive, inflicting possibly heavy losses on him, gaining time and creating conditions for the transition of his troops into an offensive or counteroffensive.
As a rule, a defensive operation is carried out as part of a front-line operation in cooperation with other armies or an army operation with forces and means in the continental theater of military operations and in coastal areas - also with the forces and means of the naval forces. A defensive operation can be carried out independently on separate operational lines. [Радянська військова енциклопедія]
In military theory, defensive operation thinking seeks to understand and appreciate the theoretical and historical background of any given war or conflict scenario facing the decision-makers at the highest level. Therefore, to fully understand strategic defense activities, analysts need to have a detailed understanding of the relevant geopolitical and socioeconomic challenges and issues that faced the nation-state or large organization being studied. [Understanding War]
Trevor N. (1968). Understanding War: Military History And The Theory Of Combat. Leo Cooper: New York. (p. 239)