The Browning High Power (“Grande Puissance”, aka GP-35) was developed by Fabrique National in Belgium, designed primarily by John Browning’s apprentice Dieudonné Saive. It began in the very early 1920s as a pistol designed for a new French Army requirement, but eventually split into two separate development tracks. By the early 1930s the French procurement process was still ongoing, but FN felt that the current iteration of their pistol (the Grand Rendement) was sufficiently mature to be a viable military sidearm. They began offering it for sale, and the Belgian Army quickly took an interest. One thousand were purchased for Belgian field trials in 1933, and with a few minor changes it was adopted by Belgium as the GP-35 in 1935.
The first guns are delivered in May of 1935, and the first troops to receive them were troops like machine gun crews, tank crews, messengers and other men who needed a weapon, but not a full-length rifle. By 1938 enough have been delivered that the specialty troops and NCOs have been fully equipped, and guns begin to go to officers, replacing things like the FN Model 1900. By the time of the German invasion in May 1940, some 30,000 – 35,000 High Powers have been delivered to the Belgian Army. In addition to this, several other military contracts were made by FN, selling the pistol to Estonia, Lithuania, Paraguay, China, and Finland. However, the Belgian orders account for the significant majority of all pre-war made High Powers.
Note that in the US, original pre-war High Powers with original stocks, 500-meter tangent sights, and serial numbers below 47,000 (no prefix) are exempted from the NFA, and are not legally considered short-barreled rifles.