Sentry’s first and most obvious role was to look out for intruders into NATO airspace. Hitherto, low flying Floggers or Fencers could be detected only at some 30 miles’ distance by the scattered mobile forward radars close to the inner German border (IGB). Now that aircraft at any height could be clearly identified at least 200 miles away, and if flying at 5,000 feet or above, 300 miles away or more, the practical implications for NATO’s air defences were startling. Warsaw Pact aircraft could be observed taking off from bases anywhere in Eastern Germany, for example, or from others half way across Czechoslovakia, or as they were flying close above the Baltic waves beyond Bornholm. Aircraft climbing to a high-transit flight level could be detected in eastern Poland and all the way across Eastern Europe as far as the Soviet border. Instead of three or four minutes’ warning of a surprise attack, Sentry could give an air defence sector headquarters, like that at Brockzeitel not far west of Dusseldorf, up to thirty minutes’ warning.
That was not all. Additional wiring had been asked for in the eighteen NATO aircraft to incorporate electronic support equipment, the peacetime euphemism for what was required to gather electronic intelligence. In 1983, after extensive debate in the Western Alliance, funding had been provided for this equipment to be installed. Thereafter, for the next two years, data on Warsaw Pact command and control procedures, surveillance radars, SAM guidance wavelengths and even individual Warsaw Pact aircraft call signs and pilot voices had been assiduously collected and fed into the system’s data banks. Indeed, the problem was not the accumulation of data, but the constant pressure on over-stretched NATO ground staff to ensure that it was all categorized, processed and fed into the seemingly limitless capacity of the new generation of computers. Perhaps, as some thought, there was too much of it all.
The Warsaw Pact, of course, was well aware of Sentry’s potential, publicized proudly as it was in the regular editions of Western military aviation journals. And, indeed, they had in 1982 deployed their own IL-76C Cooker to perform much the same function.
Under Sentry’s long shadow, the Warsaw Pact air forces had tightened signals discipline considerably, sought to decrease their air crews’ dependence on ground control and accelerated the introduction of their own digital secure communications links. Increasingly, Warsaw Pact squadrons were deployed back to central USSR for periods of intensive operational training unobserved, but there was now no way to maintain squadron effectiveness in Eastern Europe, or exercise their surface-to-air defences, without adding to Sentry’s data bank. There had been, not surprisingly, a determined attempt by the Soviet Union to mobilize public opinion in the FRG against the modification of the Geilenkirchen base to accommodate these aircraft. This had failed in 1982 in the face of patient and well-reasoned explanations by the Federal German Government of Sentry’s enormous contribution to deterrence. One thing was sure. Quick and violent counter-measures against the system could certainly be counted on if war came.
In the spring of 1985 the Sentries began to detect small but significant changes in Warsaw Pact air activity. SU-24 Fencers had been stationed in eastern Poland for four years, steadily replacing both MiG-21 Fishbeds and, latterly, early marks of SU-17 Fitters. The bulk of the Fencer squadrons, however, had remained at bases in the eastern Ukraine, in the Kiev Military District, or the Baltic Military District. In January 1985 regular rotations of the USSR-based squadrons began first to eastern and then to western Polish airfields. Sentry quickly detected the changing voices and call signs of the new crews, who were obviously very experienced. In May and June reconnaissance sorties by Foxbat G, equipped with sideways-looking and synthetic-aperture radars, and digital information instantaneous downlinks, were greatly increased along the IGB and were duly noted by the Sentries.
Throughout the spring the weapons range at Peenemunde in the GDR was used round the clock by Flogger Gs and Js during the day and by Fencers at night. Sentry could track both medium-level approaches to the range and the actual ground-attack procedures. This information was added to all the other indicators available to the Western allies which suggested steadily increasing Warsaw Pact military activity.
In mid-July the major Warsaw Pact exercise began which was to be used as cover for mobilization.
By 2359 hours on 3 August, the Sentries had watched five regiments of Hind E gunships deploy, as part of the ‘exercise’, to forward bases 30 miles from the IGB. Two regiments of SU-25 Flatfoot ground-attack aircraft had returned to their major bases north of Leipzig, which placed them in range of both the area around Fulda and the north German plain. More significantly, the intensity of the jamming now rapidly increased. Only spasmodic attempts had ever been made to jam the Sentries’ surveillance radar before. Triangulation from the three Sentries constantly on station quickly pinpointed the sources of the jamming as eight AN-12 Cubs operating in their ECM mode, cruising some 100 kilometres beyond the IGB. However, because of the narrow beam width of the Westinghouse AN/APY-1 radar installed in the E-3A Sentries and its low side-lobe characteristics, the effect on the AWACS’ radar screens was negligible and their effectiveness remained high.
The Sentries were not the only targets for the jammers: below and in front of them were the inviting targets of the NATO ground radars — static, still in process of modernization, and highly vulnerable both to direct jamming and to side-lobe penetration. One after another these reported to their sector commanders that their medium- and high-level surveillance was becoming impaired, despite rapid switching through the frequencies available to them. The effectiveness of Soviet Click jammers, long suspected, was now being confirmed.
It was at 0315 hours on 4 August, 25,000 feet over Ramstein in the Federal Republic, that the radar operators of the Sentry aircraft E-3A 504826 of 965 Squadron, detached from Tinker to USAFE (United States Air Force Europe), first saw twelve blips appear on their screens, crossing eastern Poland at 35,000 feet, apparently from the central Ukraine on a westerly heading, at a speed of just under Mach 2. Within seconds they were also spotted by the Sentries over Venlo and west of Munich and identified as Backfires. All data were flashed immediately down to COMAAFCE’s battle staff. The Ramstein, Wildenrath (RAF) and Neuburg (FRG) battle flights were immediately scrambled and climbed away to their intercept positions, still well west of the IGB. The Backfires crossed the Polish frontier into the GDR but then broke formation and in six pairs fanned out on headings in an arc towards Hamburg in the north and Bavaria in the south. All twelve were maintaining radio silence.
Then, while still 50 miles inside Warsaw Pact territory, they banked steeply and within a few seconds one after another inexplicably turned back towards Poland. The senior controller in 504826 began to express his surprise, speaking in a somewhat relaxed tone on his secure encoded downlink to his colleagues in the bunker 30,000 feet below. As they listened his voice suddenly stopped, and at the same moment the steady, friendly IFF (identification friend or foe) signal from 504826 which was being received by the two other Sentries abruptly disappeared. As subsequent events showed, even if the USAF crew had heard the warning shouted by the Dutch ECM operator in the Venlo Sentry there was little they could have done.