This Campaign period was from 2 April to 30 June 1968. The Naval air and gun fire support to operations such as Operation Silver Mace gave ground units the needed firepower while AirForce units were moved to air operations over Laos, Cambodia and North Vietnam. From 7 to 18 April, ground, air, and naval units from each of the American services, the Vietnamese Navy, and the Vietnamese Marine Corps conducted Silver Mace II, a strike operation in the Nam Can Forest on Ca Mau Peninsula. The enemy avoided heavy contact with the allied force, but his logistical system was disrupted.
Enemy air defenses caused aviators more concern for by 1968 the Communists had developed a defensive system that was well-armed, coordinated, and supported. On the ground throughout North Vietnam, South Vietnam, and Laos, the enemy trained skyward thousands of small arms, automatic weapons, and antiaircraft artillery. North Vietnam alone contained 8,000 weapons of many calibers, concentrated around key targets. Beginning in early 1965, surface-to-air missiles (SAM) were added to this defensive arsenal, and by early 1968 over 300 SAM sites dotted the North Vietnamese countryside. The entire defensive system was tied together with a sophisticated network of communications, air alert stations, and early warning, ground control-interceptor, and fire control radars. New and replacement weapons and ammunition were amply supplied by sympathetic Communist countries. The loss in Southeast Asia of 421 fixed-wing aircraft from 1965 to 1968 attested to the strength of these defenses. The aviators killed, missing, or made prisoner totaled 450. The operating environment was especially dangerous in North Vietnam, where 382 Navy planes were shot down, 58 of them by SAMs.
Although only accounting for eight of the Navy's aircraft during this three-year period, the North Vietnamese air units posed a constant threat to U.S. operations, thus requiring a diversion of vital resources for protection. The enemy air force varied from 25 to 100 MiG-15, MiG-17, MiG-19, and MiG-21 jet fighters. The country's jet-capable airfields included Gia Lam, Phuc Yen, Cat Bi, Kep, Kien An, Yen Bai, Son Tay, Bai Thuong, Hoa Lac, and Vinh. The U.S. Navy engaged in its first air-to-air encounter of the war on 3 April 1965, when several MiG-15s unsuccessfully attacked a flight of F-8 Crusaders near Thanh Hoa. On 17 June, two Midway F-4 Phantoms registered the first kills in the long conflict when they downed two MiG-17s south of Hanoi.