Fritz X was a nickname used both by Allied and Luftwaffe personnel. Alternative names include Ruhrstahl SD 1400 X, Kramer X-1, PC 1400X or FX 1400 (the latter, along with the unguided PC 1400 Fritz nickname, is the origin for the name "Fritz X"). Along with the United States Army Air Forces (USAAF) similar Azon weapon of the same period, it is one of the forerunners of modern anti-ship missiles and precision-guided weapons.