Precision-guided bomb

A guided bomb (also known as a smart bomb, guided bomb unit, or GBU) is a precision-guided munition designed to achieve a smaller Circular error probable (CEP).

Because the damage effects of explosive weapons fall off with distance according to a power law, even modest improvements in accuracy (and hence reduction in miss distance) enable a target to be effectively attacked with fewer or smaller bombs. Therefore, with guided weapons, fewer air crews are put at risk, less ordnance spent, and collateral damage reduced.

The creation of precision-guided munitions resulted in the retroactive renaming of older bombs as unguided bombs or "dumb bombs".

A guided bomb of a given weight must carry fewer explosives to accommodate the guidance mechanisms.

Guided bombs carry a guidance system which is usually monitored and controlled from an external device.

The Germans were first to introduce Precision Guided Munitions (PGMs) in combat, using the 1,400-kg (3,100 lb) MCLOS-guidance Fritz X to successfully attack the Italian battleship Roma in September 1943. The closest Allied equivalents were the 1,000-lb (454 kg) AZON (AZimuth ONly), used in both Europe and the CBI Theater, and the US Navy's Bat, primarily used in the Pacific Theater of World War II which used autonomous, on-board radar guidance. In addition, the U.S. tested the rocket-propelled Gargoyle; it never entered service. No Japanese remotely guided PGMs ever saw service in World War II.

The United States Army Air Forces used similar techniques with Operation Aphrodite, but had few successes; the German Mistel (Mistletoe) "parasite aircraft" was no more effective.

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