The Strv 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 Strv m/39 was designated L-60-S/II.

Introduced in Update 1.97 "Viking Fury", the Strv m/39 plays much like the Strv m/38: it is fast, manoeuvrable, and has excellent firepower. While it lacks APHE, it has access to a powerful APDS shell with insanely good penetration values for such a low BR tank. The new turret has increased armour, up to 50 mm thickness. Its gun handling is also great, with a good turret traverse rate and excellent gun depression of -15 degrees. However the hull has very light armour, and the small crew makes the tank vulnerable to even autocannon fire.