and better-armoured tank, also faster and better able to keep up with tanks such as the Sherman. It was armed with a 75 mm gun mounted in the hull and a 37 mm gun in a turret, so could retain some fighting capacity when the searchlight turret was mounted. A dummy gun-barrel fitted to the turret made it resemble a normal M3 tank. The operator was the only occupant of the turret—the vehicle commander had a seat to the left of the driver. The project was shrouded in secrecy. It was tested during Exercise Primrose in 1943 at Tighnabruaich, Scotland; it was concluded that it was "too uncertain to be depended upon as the main feature of an invasion". The CDL was shown to senior US officers (including generals Eisenhower and Clark) in 1942 and the US decided to produce their own tanks using the CDL design. The codenames "Leaflet" for the tank, and "Cassock" for the training programme for crews were used. For secrecy the construction was dispersed. Conversion of the M3 to take the CDL was by the American Locomotive Company as "Shop Tractor M10", turrets were produced by Pressed Steel Car Company as "coast defence turrets", and the arc lamps were sourced through the Corps of Engineers. The final assembly of the CDL tank was at Rock Island Arsenal. By the end of 1944, Alco had produced 497 tanks. American crews were trained at Fort Knox and in the California-Arizona manoeuvre area. The six battalions of tanks then moved to the UK to join the British CDL tanks in Wales. Deployment and combat The British and American CDL units deployed to the continent did not cross over to France until August, the British as part of the 79th Armoured Division. The British 35th Tank Brigade and US 9th Armored Group were retained in the UK. The system was highly secret as surprise was considered essential to its use. This hampered its employment, as commanders were often unfamiliar with, or did not know of it, and did not consider it when drawing up plans for attack. Rather than let trained tank crews sit idle, most of the special units were converted either to other special roles (such as mine clearance tanks) or regular tank units. For the crossing of the Rhine, some CDL units were used. The one British squadron that had not been converted from CDLs was