Fritz X Fritz X was the most common name for a German guided anti - ship glide bomb used during World War II . " Fritz X " was a nickname used both by Allied and Luftwaffe personnel . Alternate names include Ruhrstahl SD 1400 X , Kramer X - 1 , PC 1400X or FX 1400 ( the latter is also the origin for the name " Fritz X " ) . Along with the USAAF ' s similar Azon weapon of the same period in World War II , it is one of the precursors of today ' s anti - ship missiles and precision - guided weapons . History . The Fritz X was a further development of the high - explosive bomb SD 1400 ( " Splitterbombe , dickwandig , 1400 kg " ) . It was a penetration weapon intended to be used against heavily protected targets such as heavy cruisers and battleships . It was given a more aerodynamic nose , four stub wing s , and a box shaped tail unit , consisting of a roughly 12 - sided annular set of fixed surfaces , and a cruciform tail with thick surfaces within the annulus , which themselves contained the aerodynamic controls . The Luftwaffe recognized the difficulty of hitting moving ships during the Spanish Civil War . " Dipl . engineer " Max Kramer , who worked at the DVL , had been experimenting since 1938 with remote - controlled free - falling 250 kg bombs , and in 1939 fitted radio - control led spoiler s . In 1940 , Ruhrstahl was invited to join the development , since they already had experience in the development and production of unguided bombs . The dual - axis , single - joystick - equipped " Funkgerät ( FuG 203 ) Kehl " series of radio - control transmitter sets on board the deploying aircraft , were used to send the control signals to the Fritz - X , with the ordnance itself picking up the signals through a " Funkgerät ( FuG 230 ) Straßburg " receiver , named for the city , within it to send the signals on to the movable spoilers in the Fritz - X ' s thick vertical and horizontal tail fin surfaces , within the annular tailfin structure . The " Straßburg " receiver ' s antennas were aerodynamically integrated into the trailing edge of the annular surfaces of the tailfin , within a quartet of " bulged " sections in the trailing edge . Control setup on the Fritz X . The Fritz X possessed a spoiler - based control setup on its tailfin unit , using three sets of aerodynamic control spoiler systems , with two of them giving the ordnance control in both the pitch and yaw axes , differentially operating and oscillating under direct control from the " Kehl - Straßburg " radio control link . The roll control setup , operating autonomously and not under control from the deploying aircraft , were located on the outboard sections of the horizontal tailfin surfaces within the annular set of outer tailfin surfaces . These were like the American Azon ordnance ' s own " aileron " control surfaces , commanded by an internal gyroscope in the tail ' s central housing to keep the ordnance level during its trajectory . The inboard set of spoiler surfaces in the tailfin ' s horizontal surfaces , which used a set of wing fence - like flat surfaces for airflow separation from the autonomous roll control spoilers , controlled the pitch angle after release and were controlled by the radio control link , giving the Fritz X ' s bombardier in the deploying aircraft the ability to control the range of the drop , a capability that the Azon ordnance did not have . The yaw control spoilers housed in the vertical tailfin surfaces were also under control through the radio link , and had similar " fence " surfaces to guide airflow over them . All three spoiler surface sets , when deployed , barely protruded from the surface during operation , with the pair of spoiler systems under external control having a degree of " proportionality " in their operation by varying their rate of oscillation from side to side when a control input was sent to them . Combat service . The only Luftwaffe unit to deploy the Fritz - X was " Gruppe " III of " Kampfgeschwader " 100 " Wiking " ( Viking ) , designated III . / KG 100 , the bomber wing itself evolved as the larger - sized descendent of the earlier Kampfgruppe 100 unit in mid - December 1941 . This unit employed the medium range Dornier Do 217 K - 2 bomber on almost all of its attack missions , though in a few cases toward the end of its deployment history , Dornier Do 217K - 3 and M - 11 variants were also used . Fritz - X had been initially tested with a Heinkel He 111 bomber , although it was never taken into combat by this aircraft . A few special variants of the troublesome Heinkel He 177 A " Greif " long - range bomber were equipped with the " Kehl " transmitter and proper bombracks to carry Fritz - X and it is thought that this combination might have seen limited combat service , at least with the combinations known to have been involved in test drops . Fritz - X was first deployed on 21 July 1943 in a raid on Augusta harbor in Sicily . A number of additional attacks around Sicily and Messina followed , though no confirmed hits were made and it appears the Allies were unaware that the large bombs being dropped were radio - guided weapons . On 9 September , the " Luftwaffe " achieved their greatest success with the weapon . After Pietro Badoglio publicly announced the Italian armistice with the Allies on September 8 , 1943 , the Italian fleet had steamed out from La Spezia and headed to Malta . To prevent the ships from falling into Allied hands , six Do 217K - 2s from III . " Gruppe " of KG 100 ( III / KG 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 magazine s exploded . 1 , 255 men , including Admiral Carlo Bergamini , died . Her sister ship , " Italia " , was also damaged but reached Malta . The American light cruiser " Savannah " was hit by Fritz - Xs at 10 : 00 on 11 September 1943 during the invasion of Salerno , and was forced to retire to the United States for repairs . A single Fritz - X passed through the roof of " C " turret and killed the turret crew and a damage control party when it exploded in the lower ammunition handling room . The blast tore a large hole in the ship ' s bottom , opened a seam in her side , and blew out all fires in her boiler rooms . " Savannah " lay dead in the water with the forecastle nearly awash and took eight hours to relight boilers and get underway for Malta . " Savannah ' s " sister ship , " Philadelphia " , had been targeted earlier that same morning . While it is often believed the ship was hit by a Fritz X , in fact the bomb just missed the ship , exploding about 15 meters away . Damage was minimal . The light cruiser HMS " Uganda " was hit by a Fritz - X off Salerno at 1440 on 13 September . The Fritz X passed through seven decks and straight through her keel , exploding underwater just under the keel . The concussive shock of the Fritz X ' s underwater detonation close to " Uganda ' s " hull extinguished all her boiler fires , and resulted in sixteen men being killed , with " Uganda " taking on 1 , 300 tons of water . The " Uganda " was towed to Malta for repairs . Two merchant ships may have been hit by Fritz X bombs at Salerno , though the evidence is uncertain . SS " Bushrod Washington " was hit by a glide bomb , either a Fritz - X or a Hs 293 , on 14 September while offloading a cargo of gasoline . SS " James W . Marshall " was set afire by a conventional bomb , Hs 293 or Fritz - X on 15 September . As with the " Bushrod Washington " , the nature of the weapon that damaged " James W . Marshall " is uncertain . A witness aboard a ship nearby , Joseph A . Yannacci , attributes the attack to Ju 87 " Stuka " dive bombers , which were too small to carry glide bombs . While an attack with a Fritz - X cannot be ruled out , there is at least an equal case to suggest that , if a glide bomb was involved , the culprit was actually a Hs 293 from II . / KG 100 ; Luftwaffe records show that II . / KG 100 , armed only with Hs 293 glide bombs , was active over Salerno that day . KG 100 scored another success with Fritz - X while the British battleship " Warspite " was providing gunfire support at Salerno on 16 September . One bomb penetrated six decks before exploding in number 4 boiler room . This explosion put out all fires and blew out the double bottom . A second Fritz - X near - missed " Warspite " , holing her at the waterline . She took on a total of 5 , 000 tonnes of water and lost steam ( and thus all power , both to the ship herself and to all her systems ) , but casualties were few . She was towed to Malta by tugs " Hopi " and " Moreno " , then returned to Britain " via " Gibraltar and was out of action for near 9 months ; she was never completely repaired , but returned to action to bombard Normandy during Operation Overlord . The last Fritz - X attack at Salerno again lightly damaged the light cruiser " Philadelphia " with two near misses on 17 September . This attack is sometimes reported as taking place on 18 September . However , according to US Navy records , the cruiser " Philadelphia " departed Salerno the night of 17 / 18 September . Moreover , according to Luftwaffe records , III . / KG 100 , the Luftwaffe unit armed with the Fritz - X , flew its last mission on 17 September . Other ships damaged by Fritz - X included Dutch sloop " Flores " and destroyer " Loyal " . The control system used for Fritz - X , known as " Kehl - Straßburg " and named for Kehl , a German suburb of Strasbourg , and Strasbourg , the French / German city on the Rhine , was also used by the Hs 293 . It 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 devices which jammed the 48 . 2 MHz to 49 . 9 MHz low - VHF band radio link between the " Kehl " transmitter aboard the launching aircraft and the " Straßburg " receiver embedded in the Fritz - X ordnance . Early efforts by the U . S . Naval Research Laboratory produced the XCJ jamming transmitter installed aboard the destroyer escorts USS " Herbert C . Jones " and " Frederick C . Davis " in late September 1943 , too late for Salerno . The XCJ was ineffective because the frequencies selected for jamming were incorrect . This was updated in time for combat at Anzio with the XCJ - 1 system , installed aboard two destroyer escorts above as well as destroyers USS " Woolsey " , " Madison " , " Hilary P . Jones " and " Lansdale " . These six ships rotated service at Anzio , with three deployed at any time . This manually operated system met with some success , though cumbersome and easily overwhelmed if large numbers of weapons were deployed simultaneously . In early 1944 the UK began to deploy its Type 650 transmitter , which employed a different approach . This system jammed the " Straßburg " receiver ' s intermediate frequency section , which operated at a 3 MHz frequency and appears to have been quite successful , especially as the operator did not have to attempt to find which of the 18 Kehl / Straßburg command frequencies were in use and then manually tune the jamming transmitter to one of those frequencies . This system automatically defeated the ordnance ' s receiver regardless of which radio frequency had been selected for an individual Luftwaffe missile . Following several intelligence coups , including a capture of an intact Hs 293 at Anzio and recovery of important " Kehl " transmitter components from a crashed Heinkel He 177 on Corsica , the Allies were able to develop far more effective countermeasures in time for the invasions at Normandy and Southern France . This included an updated XCJ - 2 system from the U . S . Naval Research Laboratory ( produced as the TX ) , the modified airborne AN / ARQ - 8 Dinamate system from Harvard ' s Radio Research Laboratory , NRL ' s improved XCJ - 3 model ( produced as the CXGE ) , the Types MAS system produced by the Airborne Instruments Laboratory ( at the time affiliated with the Radio Research laboratory ) , the British Type 651 and the Canadian Naval Jammer . Even more sophisticated jammers from NRL , designated XCK ( to be produced as TY and designated TEA when combined with the upgraded XCJ - 4 ) and XCL , were under development but were never deployed as the threat had evaporated before they could be put into service . By the time of Normandy landings , a combination of Allied air supremacy , keeping bombers at bay , and ship - mounted jammers meant the Fritz - X had no significant effect on the invasion fleet . Some accounts say the Norwegian destroyer " Svenner " was hit by Fritz - X at dawn on D - Day . This is highly unlikely as III . / KG 100 , the unit which carried the Fritz - X into combat , had largely been re - equipped with the Hs 293 missile by that time for its anti - ship missions , and the attack on " Svenner " occurred before the first glide bombers launched their assaults on the Normandy beaches . Fritz - X is often incorrectly listed as having been responsible for the loss of the hospital ship HMHS " Newfoundland " at Salerno as well as the destroyer HMS " Janus " and the light cruiser HMS " Spartan " at Anzio . However , these ships were hit by Hs 293s , as clearly demonstrated by a careful analysis of Luftwaffe records regarding the deployment of III . / KG 100 , the nature of the damage inflicted , as well as reports from witnesses . ( In the case of " Janus " , either an Hs 293 or a conventional torpedo was responsible . ) The closest Allied equivalent to Fritz - X was Azon . Combat procedure . Fritz - X was steered by the bombardier in the launching aircraft 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 , and like the Azon ordnance , the Fritz - X bomb had a flare in the tail so it could be seen from the controlling aircraft for its MCLOS - form guidance to control it properly . The disadvantage with this — in comparison to self - contained glide bombs like the operational U . S . Navy ' s " Bat " radar - homing glide bomb , used against Japan in 1944 - 45 — were that the aircraft had to be flown toward the target on a steady course and that as the missile neared its target it became possible to misguide by jamming its radio channel . Unlike the Hs 293 , which was deployed against merchant ships and light escorting warships , Fritz X was intended to be used against armoured ships such as heavy cruisers and battleships . The minimum release height was and a release height of was preferred assuming adequate visibility . The Fritz X had to be released at least from the target . The plane had to decelerate upon bomb release so momentum would carry the bomb in front of the aircraft where the bombardier could see and guide it . This deceleration was achieved by making a steep climb and then level out . The bombardier could make a maximum correction of in range and in bearing . The bomber was vulnerable to fighter attack as well as ship - based air defense weapons while maintaining a slow , steady course so the bombardier could maintain visual contact to guide the bomb . When working properly , the missile was able to pierce 130 mm ( 5 . 1 in ) of armor . Accuracy is the main reason for developing a weapon system of this kind , rather than continuing to use so - called " dumb bombs " . A skilled bombardier could manage to guide 50 % of the bombs to within a 15 m ( 50 ft ) radius of the aiming point , and about 90 % hit within a 30 m ( 100 ft ) radius . ( Other sources say 60 % hits within 4 . 6 meters radius . )