VB-2 AZON/VB-3 RAZON Guided Bombs
In April 1942, the USAAF's Materiel Command (became part of ATSC (Air Technical Service Command) in 1944) began the development of the Azon family of guided bombs. The initial variant, designated VB-1, was based on a 450 kg (1000 lb) bomb (initially the M44, but later models apparently switched to the standard AN-M65), which was modified with a new tail unit. The latter consisted of a gyroscopic unit to provent the bomb from rolling, a flare for optical tracking, an octagonal shroud with control surfaces, and a radio-command receiver. When a VB-1 was dropped, the bombardier could track it through his bombsight and use a joystick-type control to send corrective commands to the bomb. The Azon guidance system allowed only lateral course corrections, but errors in range could not be corrected (hence the name Azon = "Azimuth Only").
The Azon development phase ended in late 1943, and the VB-1 was subsequently ordered into mass production. The second Azon variant was the heavier VB-2, which was based on a 900 kg (2000 lb) bomb, but that version was apparently not produced in very large numbers. The first VB-1/2 bombs were sent to Europe in February 1944, and a total of 15000 Azons were produced until November 1944.
Because of their azimuth-only guidance, the VB-1 was particularly suited to long and narrow targets (like bridges or railways) where range errors would be irrelevant. For "normal" targets, however, the VB-1 was actually not as good as unguided free-fall bombs, because a bomber could not break away immediately after dropping the bomb, and the accuracy was effectively not increased because of the lack of range control. Another peculiarity of the Azon guidance set was the fact that only five different radio channels were available for the command link, meaning that not more than five bombs could be controlled independently. Although in theory a whole group of bombs using the same command channel could be controlled simultaneously, this was not practical. The accuracy of all but the "primary" bomb (i.e. the one which was tracked by the bombardier) in such a group was rather bad, because the non-spinning Azon bombs showed a significant dispersion.
The drawbacks of the Azon meant that its use remained very limited. However, it was employed rather successfully in Burma, where it was used to destroy very vital and therefore heavily defended bridges along the Japanese supply lines. Less the 500 Azons were needed to destroy 27 bridges.
When the war ended, the USAAF quickly removed the VB-1 and VB-2 from its inventory. Because of the much reduced post-war funding, the USAAF limited its guided vertical bomb research to the more advanced VB-3/VB-4 Razon family.
The 1,000-pound Razon bomb was a remotely controlled, radio-guided bomb originally developed for use in World War II. Despite some early problems, B-29 bombardiers managed to destroy 15 bridges with Razon bombs by the end of 1950, when the much larger 12,000-pound Tarzon bomb came into use.
Although the USAF had mixed results in Korea with the Razon and Tarzon bombs, they foreshadowed the later widespread use of precision-guided weapons.
