On April 4, 1965 a strike team composed of F105 Thunderchiefs escorted by F100s took off in an air base in Thailand.
Their mission was to destroy a vital bridge which carries the main North Vietnamese rail and road artery.
The strike team was met by 4 much older "Mig 17" jets. 2 Migs jumped the lead F105 and his wingman in a slashing, diving, hi-speed GUN ATTACK, and after completing the pass, all 4 dived into the haze.

(More info:
http://www.globalaircraft.org/planes/mig-17_fresco.pl)
The toll for the mission, which left the bridge intact, was two F105 destroyed, the first US losses in air to air combat since the Korean War.
The tactics the Viets employed were believed to have come from the Soviets while the Mig 17s were supplied by China, North Korea and Russia.
Only the best pilots in North Vietnamese air force were given the chance to fly the meager fleet of Mig 17.
Among the most famous ace pilots were Capt. Nguyen van Bay who scored 7 kills by May 1966.
Another was Col. Toon (the book that i havent finished reading yet wrote it as Col Tomb) who scored 13 kills.
Vietnam never publicized any of his victory then. The US pilots concluded that he and a few other oustanding pilots must have been foreigners. Some surmised that he was a composite of several Chinese, North Korean and even Soviet pilots, who together scored this much and whose identities couldnt be publicized for reasons of diplomacy.


VPAF Aces. From left to right: Nguyen Van Bay (7 kills), Nguyen Van Coc (9) and Nguyen Doc Soat (6).
http://www.acepilots.com/vietnam/viet_aces.html