The light tank industry was a booming market following the end of World War 1 and throughout the interwar years leading up to World War 2. The Swedes forged a thriving arms industry by the end of the war and produced some fine armored fighting vehicles before then. One such vehicle became the m/31, also known as the L-10 by Landsverk - becoming the first indigenous Swedish tank venture.
Following the end of World War 1, Germany was stripped of much of its war-making material and facilities. However, this did not keep the nation from continuing to develop new weapons while keeping serviceable ones away from the prying eyes of its victors. The Germans had developed the Leichter Kampfwagen II during the war and finalized two pilot vehicles by June of 1918. While some 580 of the type were officially on order, the end of the war saw fit to cancel the motion.
The Swedish government maintained interest in the LK II and secretly paid the German government one to several thousand kronor (sources vary) for ten examples of the tank. The tanks were then shipped in pieces to Sweden and further disguised as agricultural equipment and boiler machine parts to avoid the attention of the Allied Control Commission governing the German disarmament. On the Swedish end, the vehicles were reassembled and placed into Army service under the designation of "Strv m/21" beginning in 1921. The m/21 was modestly armed with a single machine gun of 6.5mm caliber and a future variant - the m/21-29 - was devised in 1929 finally fitting a capable 37mm main gun and twin machine guns for self-defense. The type was further powered by a Swedish engine. The m/21-29 variants soldiered on into 1938 at which point it was retired from service.
Over time, operational experience soon shown that the m/21s could be improved for the better so the Swedes enlisted the help of German Joseph Vollmer. Vollmer held much experience in the design and development of armored fighting vehicles dating back to the German attempts of World War 1, particularly the A7 and the K-Wagen types designed for the German Army. Additionally, the German government went on to own a major portion of the Landsverk Company before World War 2 so the German influence in the design of the m/31 was very considerable. Three m/31 tanks were ordered in the latter portion of 1931 with deliveries not beginning until late 1935.
Externally, the Strv m/31 was of a very clean design approach unlike the boxy systems found in World War 1. Her appearance was more akin to the designs that would become commonplace in World War 2 and beyond, conventionally fitting a rear engine with a traversing turret containing the main armament. The crew compartment and turret were all held ahead of amidships while the engine was set in a rear compartment. The driver maintained a position to the front-left of the vehicle with a bow-gunner to the right manning a machine gun. The tank commander and gunner resided in the 360-degree traversing turret completed with slightly sloped sides and the main armament backed by a coaxial machine gun. The track system consisted of linked sections surrounding two sets of four rubber-tired road wheels with two track return rollers along the top, a drive sprocket at the rear and a track idler at the front. Power was supplied by a Bussing 6-cylinder gasoline-fueled air-cooled engine of 140 horsepower at 2,500rpm. This supplied the chassis with a top speed of 25 miles per hour and an operational range of 125 miles. Like other Swedish tanks, the suspension system of the Strv m/31 was excellent and encouraged off-road travel.
Primary armament for the type was a 37mm (1.46") main gun fitted to the turret. A coaxial 7.7mm machine gun was fitted next to the main gun mount and operated by the gunner. A second 7.7mm machine gun was fitted to an emplacement in the front-right hull to be operated by a dedicated machine gunner alongside the driver. All told, the m/31 packed quite an offensive punch for the little tank considering many of her counterparts were still fielded only machine gun armament at the time.
The Landsverk Company drove production of the m/31 which began replacing the earlier - and now outmoded - m/21s in Army service beginning in 1931. m/31s, on the whole, led a limited service life in the Swedish Army.