6-16. The defense concept requires that units in defensive positions accomplish their mission independently or in combination by defeating the enemy by fire, absorbing the strength of the attack within the position, or destroying the enemy with a local or major counterattack. Commanders combine the advantages of fighting from prepared positions, obstacles, planned fires, and counterattacks to isolate and overwhelm selected enemy formations. Commanders must be prepared to rapidly shift the nature and location of their main efforts, repositioning units to mass fires against the attacker to prevent breakthroughs or preserve the integrity of the defense.