According to Wikipedia, Not to be confused with the later (1935) Karabiner 98k, the Karabiner 98a (K98a) was a shorter version of the Gewehr 98 originally made for cavalry and support unit use. The original model Karabiner 98, with a shorter barrel than the G98, was produced from 1899–1908, but it was not successful. In 1908, the Karabiner Model 1898AZ was approved. The "AZ" stands for "Aufpflanz-und-Zusammensetzvorrichtung".[9] The new features were a small diameter receiver ring, tapered rather than stepped barrel contour, an L-shaped stacking rod attached to the stock near the muzzle, a turned-down bolt handle and recess in the stock in the same fashion as sniper Gewehr 98s. The "A" stood for "with bayonet", the "Z" stood for stacking pyramid, meaning carbine Model 1898 with bayonet attachment point and stacking rod device.

During World War I, the Karabiner 98a was issued to cavalry, to mountain troops, and later to "established" assault units. It was liked because it was lighter and shorter than the Gewehr 98, and was thus better suited for use in trench assaults.