During the cold war we knew nothing about USSR aircrafts but that what NATO propaganda issued. A lot of this old information is still around. After the break down of USSR a lot of new information was available. Today we know a lot about all the now gone aircrafts of the old USSR. This one is the Tu-126, a former AWACS of the USSR. It was one of the first of such aircrafts and flew first in 1964. NATO knew nothing about this aircraft and it was not until 1968 that it get attention to it. The Tu-126 was not so sophisticated like the E-3 AWACS. It was simple but it did it's job. It's job was to detect incoming bombers from the north route, the shortest route from USA to USSR. Tu-126 was not able to detect aircraft against surface clutter from higher flying heights but because the long ranges, Russia is huge, incoming bombers had to fly in economic heights to preserve fuel and went into low flying just before entering Soviet airspace. So the shortcomings of the Tu-126 were regardless. But in heights of 5.000 meters it could detect low flying aircrafts too. The Tu-126 worked together with the interceptor Tu-128. It had a data link to a surface station and was so part of the early warning network. It could operate out of 2000 km around such a station and 1000km out of Soviet air space and give the forces time of 3 hours to react. In 1982 it was replaced by the more modern A-50 and the Tu-128 interceptor was replaced by the much more modern MiG-31. But the Tu-128 was an interesting piece too. It's Smerch-M was one of the most powerful radar sets of it's time with a look down capability. To use this new capability the Tu-128 was equipped with the newer R-4RM missiles (NATO code AA-5 Ash).