The Light Tank M2 series was the most important pre-war US tank. These light tanks were mechanically very reliable, with good mobility. However, they had a high silhouette — from the use of an air-cooled radial engine for power — and poor armor. Only a few saw combat, on Guadalcanal. Their importance lies in the fact that they formed the basis for the much more successful Light Tank M3 (a.k.a. 'Stuart' in British service) series beginning in 1941. The M3 Light Tank was an improvement of the M2 Light Tank, with heavier armor and a 37 mm gun. From the M3A1 version, this gun was gyrostabilized.