Today, air forces of all major nations are equipped with guided bombs (precision-guided munitions or “smart bombs”). The first such weapon – FX 1400 (better known as Fritz X) – was developed (by Ruhrstahl), deployed and successfully used in combat by the Luftwaffe of Nazi Germany.
Although Fritz X was first deployed on 21 July 1943 in a raid on Augusta harbor in Sicily (then invaded by the Allies), its biggest success was achieved on September 9th of the same year.
After Pietro Badoglio publicly announced the Italian armistice with the Allies on 8 September 1943, the Italian fleet had steamed out from La Spezia and headed to Tunisia. To prevent the ships from falling into Allied hands, six Do 217K-2s from III. Gruppe of Kampfgeschwader 100 took off, each carrying a single Fritz X.
The Italian battleship Roma, flagship of the Italian fleet, received two hits and one near miss, and sank after her magazines exploded. 1,393 men, including Admiral Carlo Bergamini, died. Her sister ship, Italia, was also seriously damaged but reached Tunisia.
Fritz X was a further development of the PC 1400 armor-piercing high-explosive bomb. It was a penetration weapon intended to be used against heavily armored targets such as heavy cruisers and battleships. When working properly, the missile was able to pierce 130 mm armor.
Fritz-X was steered by the bombardier in the launching aircraft (Dornier Do 217K-2 medium bomber) over a radio link between the aircraft’s Kehl transmitter and the weapon’s Straßburg receiver.
The bombardier had to be able to see the target at all times, so the Fritz-X bomb had a flare in the tail so it could be seen from the controlling aircraft for its guidance system to control it properly. A skilled bombardier could manage to guide half of the dropped bombs to within a 15 m radius of the aiming point, and achieve about 90% hit within a 30 m radius.
The control system used for Fritz X relied on radio contact between the bomb and the guidance unit, and was susceptible to electronic countermeasures. After the initial attacks in August 1943 the Allies went to considerable effort to develop jamming devices.
These were first deployed in late September 1943 and by the time of the Normandy landings, a combination of Allied air supremacy (keeping the Luftwaffe’s bombers at bay) and ship-mounted jammers meant Fritz X had no significant effect on the invasion fleet.