The M.W.S.D. hoped to build about 1600 new Heavy Tanks, 800 of which were to be of the Mark V. type and ready by May 1, and the others to be of other heavy types, probably Mark V. star and Mark VI., while 385 Whippet (“Medium A”) Tanks were also to be ready by May 1918. Further, there was to be a small cadre of Salvage Tanks and of special infantry Supply Tanks, two of the latter being able to carry complete supplies for an infantry Brigade for one day. A large number of these Tanks were as before to be built by the Metropolitan Carriage and Wagon Company. A very brief account of most of these new types of Tank has already been given in Chapter I., and it is not necessary to repeat here the details of their speeds, armament, and so forth. Salvage Tanks were usually Mark IV. Tanks on which special gear, such as winches and small cranes, had been fitted for hoisting wrecks out of the mud, or for towing. The Supply Tank was a Mark IV. fitted with very capacious sponsons. In order to save weight these carriers were not made as fully armoured as the fighting Tanks. The Gun Carrier Tank was a machine with an elongated tail which formed a platform whence it was intended that a 60-pounder gun or a 6-in. howitzer could be fired. The Tank Corps Armoured Cars were of the usual turreted pattern, and were armed with machine-guns. But more important than any other new development was the improvement in the main issue of heavy Tanks, an improvement which is very well described by the historian of the 13th Battalion: “The old Mark IV. type had serious disadvantages. Its engine power on bad ground was insufficient, and the clumsy secondary gears made turning slow and difficult as well as requiring the services of at least two members of the crew in addition to the driver. This, in battle, became a heavy handicap upon the fighting powers of the Tank. The officer was hampered by the need to attend to brakes, and a gunner called upon suddenly to help alter gears would lose the fleeting chance of firing at favourable targets. In the new Mark V. Tank these troubles largely disappeared. An engine of new design gave both greater speed and greater turning power, while a system of epicyclic gears made turning easy and under the sole control of the driver. The officer was free to supervise his crew, the gunner was free to use his weapons to the best advantage. Add that a greatly increased field of view was obtained by the addition of an observer’s turret, and it will be understood that an immense advance in type had been secured.” The Mark V. had, however, one serious drawback. Its ventilation was extremely faulty. We shall see later how serious a disadvantage this was to prove. III There were also to be changes in the technical and mechanical engineering side of the Tank Corps itself, by which an economy of man-power was to be effected.