were discarded from the establishments of British armoured divisions as not suitable for further service. The Tetrarchs remained in Britain, and would probably have been used as training vehicles before being retired from service, but on 22 June 1941 the German invasion of the USSR, Operation Barbarossa began, and the USSR became an ally of Britain. The Lend-Lease program, begun in March 1941 by the United States of America to supply defensive materials to Britain and China, was therefore extended to the USSR. As part of the program, the British government began supplying war materials to the USSR, which in early 1942, included a shipment of 20 Tetrarchs, as well as a number of Valentine and Matilda Mk I Infantry tanks. The Soviet military utilised a greater number of light tanks than the British, and so could use the Tetrarchs. When the tanks arrived in the USSR, however, it was apparent that the design problems with the cooling system were also present in cold conditions; additionally, the cold weather had a deleterious effect on the tank's suspension and tracks. Additional testing of the Tetrarchs was conducted by the Soviet military and the design was admired for its controllability, manoeuvrability, and speed, as well its ability to run on low-quality fuel, unlike contemporary Soviet designs. The thinness of the Tetrarch's armour was found to be a problem and one which could not be solved, as the weight of extra armour plating caused an unacceptable reduction in the tank's speed. Despite these drawbacks in the Tetrarch's design, Soviet authorities believed it to be comparable to the T-70 light tank in use at the time, and decided that it was suitable to be used in combat. A number of Tetrarchs were sent to Tank Training Schools which were subsequently sent into battle, and in September 1943 two were assigned to the 132nd Separated Tank Battalion, which was attached to the 5th Guards Tank Brigade; both tanks were destroyed in combat, one on 30 September and the other on 2 October, the latter a casualty of artillery fire. Several were also used for propaganda purposes, appearing in photographs of Soviet troops who were fighting in the Caucasus region. Operation Ironclad In mid-1941, the Royal Armoured Corps in Britain created three tank squadrons for special overseas operations, known as 'A', 'B' and 'C' Special Service Squadrons. Both 'A' and 'B' Squadrons were equipped with Valentine