Official Designations: Commonly known as Ruhrstahl X-1, FX-1400, or PC 1400 X.
Development Background: Led by Dr. Max Kramer, development began in 1938–1939 with the aim of solving the problem of bombers being unable to hit moving ships.
Physical Specifications: Modified from the PC 1400 armor-piercing bomb, weighing approximately 1,400 kg (over 3,000 lbs), with a warhead of about 300 kg.
Guidance System: Used "Kehl/Strasbourg" radio command guidance. The operator in the carrier aircraft visually tracked a flare in the tail of the bomb and sent correction commands via a joystick.
Control Method: Course changes were made through spoilers on the cross-shaped tail fins, controlled by solenoid valves.
Release Conditions: Typically carried by Do 217 bombers and released from an altitude of 4,000 to 5,000 meters. Visual contact had to be maintained throughout, making it vulnerable to clouds and smoke.
First Combat Use: First used against Allied ships in the Mediterranean on August 29, 1943. Initially, the Allies did not even realize the bombs were guided.
Peak Engagement (Sinking of the Roma): On September 9, 1943, the German Air Force used the bomb to attack the Italian fleet sailing to surrender to the Allies. The battleship Roma was hit, its magazine exploded, and it sank, killing 1,254 officers and men; its sister ship, the Italia, was also severely damaged.
Other Results: During the Salerno landings, it severely damaged the British battleship Warspite, putting it out of action for a full year.
Fritz X's drawbacks were equally clear: after releasing the bomb, the carrier aircraft had to remain on a straight and level course, making it an easy target for Allied fighters; moreover, the radio commands were highly susceptible to jamming. As Allied jamming equipment was put into use, its hit rate dropped sharply. It was eventually discontinued in late 1944, and its combat career ended in April 1945 after being used to bomb bridges on the Oder River.