The 9x18mm Ultra was the result of a collaboration between Gustav Genschow and Company (GECO) and Walther Arms in the 1930's. The German Air Force requested a replacement for the .32 ACP. The .32 ACP at the time was the most widely used cartridge for military pistols in Germany, and many felt performance was lacking when compared with other available cartridges. The 9mm Ultra was expected to provide a more powerful cartridge suitable for use by the military. Cartridge development was set aside as Germany descended into World War II.
The 9X18 Ultra shares ballistic properties similar to those of the 9x18 Makarov. The most common load propels a 100 grain bullet at a velocity of 1,050 feet per second at the muzzle. This did not make it a stellar performer, but it was a dramatic improvement over the ballistics of the .32 ACP cartridges being used at the time. These numbers, however, approximately matched the performance of the already well-established .380 ACP. It is likely that this issue is what kept the 9mm Ultra from earning a stronger following.
Walther revived the cartridge in 1972 with the introduction of the PP Super, a model of their PP pistol. The pistol was chambered in 9x18 Ultra, but they renamed the cartridge the 9x18 Police. Several other companies from Germany and Italy began to produce pistols and cartridges made for law enforcement agencies. The German police, unfortunately for GECO and Walther, decided to adopt the for their duty side arms the 9x19mm Luger cartridge. Sales of the 9x18 dropped sharply as a result, and soon, Walther stopped manufacturing pistols in this caliber. No one has since attempted to revive the cartridge. Fiocchi currently offers the 9x18 Ultra with one load configuration and marketed with the "Police" name. No other large manufacturers make sizable quantities of 9x18mm Ultra ammunition.