Precision-guided munition

A precision-guided munition (PGM), also called a smart weapon, smart munition, or smart bomb, is a type of weapon system that integrates advanced guidance and control systems, such as GPS, laser guidance, or infrared sensors, with various types of munitions, typically missiles or artillery shells, to allow for high-accuracy strikes against designated targets. PGMs are designed to precisely hit a predetermined target, typically with a margin of error (or circular error probable, CEP) that is far smaller than conventional unguided munitions. Unlike unguided munitions, PGMs use active or passive control mechanisms capable of steering the weapon towards its intended target. PGMs are capable of mid-flight course corrections, allowing them to adjust and hit the intended target even if conditions change. PGMs can be deployed from various platforms, including aircraft, naval ships, ground vehicles, ground-based launchers, and UAVs. PGMs are primarily used in military operations to achieve greater accuracy, particularly in complex or sensitive environments, to reduce the risk to operators, lessen civilian harm, and minimize collateral damage. PGMs are considered an element of modern warfare to reduce unintended damage and civilian casualties. It is widely accepted that PGMs significantly outperform unguided weapons, particularly against fortified or mobile targets.

During the Persian Gulf War guided munitions accounted for only 9% of weapons fired but accounted for 75% of all successful hits. Despite guided weapons generally being used on more difficult targets, they were still 35 times more likely to destroy their targets per weapon dropped.

Because the damage effects of explosive weapons decrease with distance due to an inverse cube law, even modest improvements in accuracy (hence reduction in miss distance) enable a target to be attacked with fewer or smaller bombs. Thus, even if some guided bombs miss, fewer air crews are put at risk and the harm to civilians and the amount of collateral damage may be reduced.

The advent of precision-guided munitions resulted in the renaming of older, low-technology bombs as "unguided bombs", "dumb bombs", or "iron bombs".

Some challenges of precision-guided munitions include high development and production costs and the reliance of PGMs on advanced technologies like GPS make them vulnerable to electronic warfare and cyberattacks.

Recognizing the difficulty of hitting moving ships during the Spanish Civil War, the Germans were first to develop steerable munitions, using radio control or wire guidance. The U.S. tested TV-guided (GB-4), semi-active radar-guided (Bat), and infrared-guided (Felix) weapons.

The Germans were first to introduce PGMs in combat, with KG 100 deploying the 3,100 lb (1,400 kg) MCLOS-guidance Fritz X armored glide bomb, guided by the Kehl-Straßburg radio guidance system, to successfully attack the Italian battleship Roma in 1943, and the similarly Kehl-Straßburg MCLOS-guided Henschel Hs 293 rocket-boosted glide bomb (also in use since 1943, but only against lightly armored or unarmored ship targets).

The closest Allied equivalents, both unpowered designs, were the 1,000 lb (450 kg) VB-1 AZON (from "AZimuth ONly" control), used in both Europe and the CBI theater, and the US Navy's Bat, primarily used in the Pacific Theater of World War II — the Navy's Bat was more advanced than either German PGM ordnance design or the USAAF's VB-1 AZON, in that it had its own on board, autonomous radar seeker system to direct it to a target. In addition, the U.S. tested the rocket-propelled Gargoyle, which never entered service. Japanese PGMs—with the exception of the anti-ship air-launched, rocket-powered, human-piloted Yokosuka MXY-7 Ohka, "Kamikaze" flying bomb did not see combat in World War II.