The Italian military went into WWI having already adopted a semiautomatic sidearm - the Model 1910 Glisenti (and its somewhat simplified Brixia cousin). However, the 1910 Glisenti was a very complex design, and much too expensive to be practical for the needs of the global cataclysm that was the Great War. In response to a need for something cheaper, Tulio Marengoni of the Beretta company designed the Model 1915, a simple blowback handgun chambered for the 9mm Glisenti cartridge.
Only 15,300 of the Model 1915 pistol were made, because even they proved to be a bit more than the military really needed. One of their most interesting mechanical features is a pair of manual safeties - one on the back of the frame to lock the hammer and one on the left side to block the trigger. This proved a bit redundant, and the gun overall was rather large and heavy. In 1917 a scaled-down version in .32 ACP (7.65mm) was introduced which would be produced in much larger numbers. The 1915/17 would also omit the rather unnecessary hammer safety.
It is important to note that while the 9mm Glisenti cartridge is dimensionally interchangeable with 9x19 Parabellum, pistols designed for the Glisenti cartridge should never be used with standard 9x19 ammunition, as it is nearly 50% more powerful than the Glisenti specs, and doing so will quickly cause damage (and potentially catastrophic failure).