The first attacks launched under ROLLING THUNDER were less than overpowering; this was in part because the structure for delivering them in full force was not yet in place, and in part because they were launched in unsettled weather as the dry monsoon gave way to the clouds and rain of the wet, southwest monsoon. More basically, the political constraints imposed by the strategy of graduated escalation dictated a bomb line that would creep gradually up from the south until the North Vietnamese gave in. However, as the bomb line moved north, the communists showed no inclination to negotiate; instead, the scope and sophistication of North Vietnamese defenses increased. On 4 April, MiG- 17s engaged a flight of F-105s that were attacking the Dragon's Jaw bridge near Thanh Hoa and shot down two of their number. The next day, an RF-8 reconnaissance aircraft from Coral Sea obtained photographs of a SAM site under construction fifteen miles southeast of Hanoi; it was the first of many such constructions.
Washington's response to the strengthening North Vietnamese defenses was symptomatic of future responses. The President refused to permit attacks on the MiG airfields and rejected impassioned pleas from military commanders to attack the SAM sites before they could become operational; word went out that they were to be struck only if they fired on U.S. aircraft, apparently in vain hopes of a quid pro quo. The first aircraft to be lost to a SAM went down on 24 July, but attacks on the sites were only authorized three days later. The early attacks on SAM sites, tightly controlled from Washington and therefore predictable, produced heavy tosses on the American side; these were not just to SAMs, but to the radar-controlled AAA, heavy automatic weapons and small arms which ringed the batteries. Indeed, U.S. aviators quickly learned that they could outmaneuver the missiles - if they could see them in time - and the main effect of the SA-2 was to force attacking aircraft down to medium and low altitudes, where they fell prey to AAA and small arms.
The Air Force and Navy response to the SA-2 was both technological and tactical. The Navy had the Shrike in service by mid-August, but the development of appropriate tactics took time and the first successful attack on a SAM site, by a flight of A-4s led by an A-6, was not until 17 October. The Air Force fitted B-66 bombers with powerful transmitters to jam communist early warning and ground-controlled intercept (GCI) radars and developed jamming pods for fighters which denied range information to SA-2 radars. Next came cockpit-mounted radar warning devices. Finally, the Air Force developed specialized anti-missile hunter-killer aircraft, modified two-seater F-OOFs and later F-105Gs, with an electronic warfare officer (EWO) in the rear seat monitoring an array of radar detection equipment. Called IRON HAND generically and Wild Weasel by the Air Force, hunter-killer flights led by such aircraft successfully limited the SA-2's effectiveness. This success, however, was gained at a price, both in human terms, for IRON HAND duty was dangerous, and economically, for the equipment was expensive. Similarly, the Air Force and Navy put considerable effort into their attempts to shoot down MiGs, eventually achieving respectable kill ratios after a disappointing start. But, as with the SA-2, the main effect of the MiGs was to divert American resources.