The T-26 began as a Soviet adaptation of the British Vickers 6-Ton, but its design quickly diverged to suit the Red Army's needs. The earliest T-26, the 1931 model, kept the British twin-turret layout, each mounting a machine gun. Soviet designers, however, modified the turrets, raising them for better visibility and fitting them for Degtyarev light machine guns instead of Vickers guns. The hull was built with riveted armour plates, later supplemented with welding in some vehicles. At 13–15 mm thick, the armour was enough to stop small-arms fire, but it left the tank vulnerable to heavier weapons. The twin-turret design soon showed limitations, as its firepower could not be concentrated on a single target. In 1933, the Soviets introduced a major redesign: a single cylindrical turret carrying a 45 mm 20K cannon alongside a coaxial 7.62 mm machine gun. This gun, derived from the Soviet 45 mm anti-tank gun, gave the T-26 an edge over contemporary light tanks and even posed a threat to early anti-tank positions. Up to three additional machine guns could be fitted, one in the turret rear and another in an anti-aircraft mount. This single-turreted version became the most common T-26 variant. The T-26 was powered by the GAZ T-26 engine, a Soviet-built copy of an Armstrong Siddeley design. Early engines were unreliable and prone to overheating, but production quality improved after 1934. With around 90 horsepower, the tank could manage modest speeds and had a range of about 120 km. Its suspension used paired bogies with leaf springs, while a front drive sprocket and rear idler kept the tracks in motion. Though relatively simple, this setup gave the tank decent cross-country ability. It could climb gradients, ford shallow streams, and cut through obstacles like small trees, making it practical for infantry support. By 1937, designers began upgrading the T-26 with improved sights, radios, and new features such as rear-facing machine guns and anti-aircraft mounts. Searchlights were added for night combat, and ammunition storage was increased. In 1938, the cylindrical turret gave way to a conical version, which offered better ballistic protection, though the armour remained thin by late-1930s standards. After combat experience at Lake Khasan in 1938 revealed weaknesses, the T-26 received sloped armour and thicker plates in 1939, resulting in the T-26 mod. 1939. These improvements were modest, as the basic design had reached its limits. Although versatile and produced in large numbers, the T-26's thin armour and light construction meant it became obsolete as anti-tank weapons advanced. By the early 1940s, the T-26 was already outclassed, but it remained in service due to its numbers and reliability. Its gradual series of design updates reflected the Soviet attempt to stretch a 1930s light tank into a rapidly changing battlefield dominated by heavier, more modern machines.