Our unit has 1 of these powerful AA guns in operation. Germany produced a series of 37 mm guns prior to and during World War II as their primary medium-caliber anti-aircraft gun.

The original 37 mm gun was developed by Rheinmetall in 1935 as the 3.7 cm Flugzeugabwehrkanone 18. It was essentially an enlarged version of the 2 cm FlaK 30 firing a 37 mm shell from an L/89 barrel. Like the Flak 30, it used a mechanical bolt for automatic fire, but nevertheless featured a fairly good rate of fire, about 160 rounds per minute. The complete gun, including the wheeled mount, weighed 1,757 kilograms (3,870 lb).

The Flak 18 was produced only in small numbers, and production had already ended in 1936 in favor of well known 2 cm Flakvierling 38, a four-barrel development of the Flak 30. Development continued, however, resulting in a lighter two-wheel mount produced as the 3.7 cm Flak 36 that cut the complete weight to 1,544 kilograms (3,400 lb). A new sighting system introduced the next year produced the 3.7 cm Flak 37 that was otherwise similar. It appears existing weapons were brought up to the Flak 37 standard, while new production started in 1942 and produced 1178 before production ended in 1944.