Defence in depth
A similar tactic is called a delaying action. The object is for a smaller force to harass a larger force to delay its advance, and to inflictil as much damage as possible to the larger force without directly engaging it. That allows the defending army's main force to disengage an enemy and to maintain good order. The main force is given the time necessary to set up a new defensive position. The small force protecting the larger force is called a rearguard.