7-122. During the performance of offensive tasks there may be enemy counterattack penetrations into the flanks of advancing divisions and BCTs. The divisions and BCTs employ security forces on exposed flanks to provide early warning and reaction time. If flank security forces cannot defeat or fix enemy counterattacks, Divisions and BCTs affected by these enemy counterattacks quickly transition to a defense or a delay. The corps or division commander determines size, composition, direction of attack, probable objective, and rate of movement of the counterattacking enemy force. This allows the corps or division commander to assess risk and develop courses of action to defeat the counterattacking enemy force. These courses of action will employ a mix of dynamic defensive actions to turn the enemy force into engagement areas and block its further advance. This may require changing task organization. It will require adjusting subordinate unit boundaries, assigned missions, and control measures. The commander directs the execution of situational or reserve obstacles, the shifting of priority of fires, and the assumption of risk. Corps and division commanders employ offensive actions to isolate and destroy a counterattacking enemy force once it is fixed in these engagement areas.