The attacks on North Vietnam proved so ineffective, mainly because of political restrictions, that in 1968, after three years of offensive, and at the urging of the U.S. Army and Marine Corps, the U.S. Navy returned to service the battleship Missouri equipped with 405 mm guns. The operation cost the price of six F-4s.
More than 1000 objectives on the North Vietnamese coasts came within range. Missouri was withdrawn just before the big communist offensive of April 1972, when her formidable firepower, especially along the demilitarized zone (between the two Vietnams), would have been of great use. For the Americans, the only positive aspect of the situation in 1968 besides the disappearance of the Viet Cong and the fact that the North Vietnamese regular army was now operating in the South almost "officially" - concerned the surface-to-air missiles SAM-2, which had proven to be very inaccurate:particularly vulnerable to ECM jamming, they could even be avoided by the target aircraft.
The North Vietnamese Air Force deployed MiG-21s without ever questioning American air superiority. Nevertheless, the few results obtained in the air were far from the overwhelming American superiority in Korea. They also brought about a real revolution in air combat techniques.