QRF (Quick Reaction Force)
This is a generic term used to identify reinforcements that can enter your AO upon short notice and change the tactical situation. Along the Ho Chi Minh trail, small groups of VC are moving material, patrolling, or regrouping prior to crossing the Laotian border for an attack.
Although somewhat more careless on the trail than when they are operating in South Vietnam, the Viet Cong are consistent in their ability to move in and out of an AO in a flash. When there is commotion, the Viet Cong are known to quickly organize and hit the area and flood it.
The QRF will be deployed after any commotion in the area (eg. explosions, firefights, insertion or hostiles alerted to the Rangers' presence) and can take up to 6 real-time minutes to arrive. The unit will then search the area where the last disturbance has taken place. If a QRF has been sent to enter your AO, no additional QRF will be committed until the active QRF has deployed. This means that the enemy can deploy a large amount of troops to the area if the commander causes too much trouble.