"The introduction of the B-52 into the Vietnam war brought an incredibly devastating weapons system within the control of ground force commanders.  However, the delivery accuracy was often limited by a complete lack of cultural radar returns and suitable geographic points.  To solve this problem, SAC began using ground based radar equipment operated by the 1st Combat Evaluation Group (CEG) to direct aerial bombing raids.  This tactic was labeled Ground Directed Bombing (GDB) and given the code name COMBAT SKYSPOT.  CEG personnel would guide the bombers along a designated route and, at the proper moment, signal the aircrew to release their weapons.  COMBAT SKYSPOT not only provided flexibility in targeting, but its accuracy soon surpassed that of the B-52.  In fact, these GDB sites were so formidable, the enemy conducted daring raids to eliminate them or force their relocation.  During their 90 month period of service in Southeast Asia, COMBAT SKYSPOT crews directed over 300,000 USAF, Navy, Marine and RVN re-supply, reconnaissance, rescue, and tactical air missions, as well as 75 percent of all B-52 strikes."