The Finns developed the M-series (26, 31, 32, and 37-39) Suomi ,equivalent of Finland', submachinegun (SMG) after the conclusion of World War I and developed this battlefield-tested, accurate and reliable (although expensive) SMG into the mid-1940s.

The Suomi prototype was developed by Finland's Aimo Lahti in 1922. Four years later, the Finnish designer rolled out the Model 31 (M/31), chambered for 7.65x22 Luger/Parabellum, for the Finnish army. In 1931, Finland's army adopted the Lachti design, alternately known as the Model 1931 or KP-31-Konepistooli ('automatic pistol'). The M/31 was manufactured by Tikkakoski Oy of Finland and licensed to Madsen (Denmark), Husqwarna (Sweden) and Hispano Suiza of Switzerland.

It should be noted that Denmark, Sweden and Switzerland produced variants of the M-series-with varying barrel and stock lengths-for different applications.

The Suomi became a complement of the Finnish and Swedish armies and it was exported to the Baltics, Europe and South America and saw action during World War II.

This SMG weighed a hefty 4.6 kilograms (10.14 pounds) empty, 7 kilograms (15.5 pounds) loaded (with a 71-round, drum filled with 9x19 mm Luger/Parabellum).

Most Suomi SMGs are 870 mm (34.25 inches) long with 314-mm (12.36-inch) barrels (the M/37-39, produced under Swedish license, featured a short barrel; the M/32 SMG was another exception, featuring no butt stock, only a pistol grip). It has an impressive, 900-round-per-minute rate of fire and is effective to 200 meters (656 feet).

The Suomi-series SMG is a blowback operated, selective fire weapon that fired from an open bolt. Magazine capacities varied (according to country of use and application) to include 20-, 36- and 50- round box and 40- and 71-round drum magazines.

Production of the Suomi M-series ended with the conclusion of World War II, however, the weapon was around into the 1990s when it was relegated to history's scrap pile (or weapons collections), replaced with the advent of the modern assault rifle.