<p>Seventh Air Force, annoyed by the frequent attacks by NVAF MiGs, decided to try a Korean War-style sweep, a mass formation of USAF fighters that would head north to try to get the NVAF, by then strengthened by some new MiG-21s, into the air where it could be hurt badly, if not destroyed. Colonel Robert F. Olds, an ace in World War II and in his second shooting war with the USAF, was given responsibility for planning the sweep—Operation Bolo—in detail. Olds, who commanded the 8th Tactical Fighter Wing, designed the sweep so that it would appear to the NVAF like any other routine strike: a standard formation of F-105s and F-4s, with escorts and Iron Hand flights, but he planned to make the entire force F-4s and only simulate the strike formation. They would get ready to fight at about the point where the F-105s would begin their steady bomb run and the MiGs would begin their interceptions. Olds' scheme called for two groups of F-4s, one coming in high from Laos, to fight the high-altitude MiG-21 patrols, and the other low from the Tonkin Gulf, to take on the MiG-17s that orbited nearer the ground. The force from Laos also would be able to intercept any MiGs trying to make a run for the Chinese border sanctuary.
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<p>Twenty flights (80 aircraft) headed out from their bases on 2 January 1967, but weather walled out the strike from the Gulf of Tonkin. Only the Laos-based planes got through, and met MiGs popping up through the overcast. In a fast and furious fight, seven MiGs were shot down at no loss to the F-4s. Olds himself got two of the enemy.
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<p>It had been the largest air engagement of the war until then, and it was to remain that. Four days later, the NVAF lost two more MiG-21s in a lesser air combat; the shock must have been traumatic, because they seemed to drop out of action altogether for an while to reconsider their tactics.
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<p>Seventh AF also reconsidered the situation, and decided that the threat justified the use of dedicated escorts. From then on, some F-4s were assigned to fighter escort, and they were used to cover attack forces headed north. It was basically the same job that the Mustangs had done in 1944 and that Sabres had done in 1951. Typically, there would be a bombing force of 16 F-105s, with an escort of two flights of four F-4s each, ahead of and behind the main formation, continuously weaving to cover the strike.
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<p>Their early tactics were to stay with the formations and deflect the MiG attacks. Later, they were free to chase and fight the NVAF opposition, a task much more to the liking of the aggressive fighter pilots.
