In warfare, it is a military tactic to defend against a mobile armoured attack, or blitzkrieg. The defenders deploy in depth in heavily fortified positions suitable for all-around defence. The attackers can penetrate between the "hedgehogs", but each position continues to fight on when it is surrounded. That keeps large numbers of attacking troops tied up, attacking the well-defended strongpoints, and it allows the defenders to counterattack against the units that bypass the strongpoints with their own armored reserves, by cutting them off from their supporting elements.
