The Stridsvagn m/39 was ordered in 1939 by KAF, that saw how new tank designs were shaping the battlefield, and the m/38 was considered to be too weak in terms of armour. The m/39 would have been a minor upgrade to its predecessor, with upgraded armour and other minor changes. AB Landsverk was against it however, since the m/38s hull was not able to sustain the increased weight. In the end, the turret was slightly modified, it included a new fire control system, as well as a lever steering system which was more favourable. While the m/38 was named L-60-S, the Stridsvagn m/39 was designated L-60-S/II.

It was introduced during Update "Starfighters" as a reward for watching War Thunder streams on Twitch.tv along with a unique skin for the vehicle. This vehicle shouldn't be confused as a tank destroyer (TD) by its designation, TD in this case stands for Twitch Drop. It has the same exact gameplay style as the Strv m/39, with access to good mobility and excellent firepower in the form of a good APDS shell. The turret's armour is increased to 50 mm of thickness, the gun depression is great with -15 degrees but the hull armour and cramped crew compartment make the tank extremely vulnerable to even autocannon fire.