rollers, Walter Gordon Wilson's epicyclical transmission from the Mark V and a V12 Rolls-Royce Eagle aero-engine. A top speed of about was reached. This project made Johnson the best qualified man to develop the later fast Medium Mark D, which looks like a reversed Medium A. Other experiments included the fitting of a large trailing wheel taken from an old Mark I tank and attaching a climbing tail, in both cases attempts to increase trench-crossing ability. For a time it was assumed that after the war some Whippets were rebuilt as armoured recovery vehicles, but this was not the case. The Medium Mark B, a completely different design by Wilson, also had the name "Whippet". For a time it was common to describe any of the lighter tank designs as a Whippet, even the French Renault FT. It had become a generic name. The German Leichter Kampfwagen — developed from December 1917 — being also a turret-less tank with the engine in front resembled the Whippet, but was a smaller vehicle with thinner armour. Combat history Whippets arrived late in the First World War, at a time when the British Expeditionary Force, recovering from the Third Battle of Ypres in Flanders, was quite inactive. They first went into action in March 1918 and proved very useful to cover the fighting withdrawal of the infantry divisions recoiling from the German onslaught during the German spring offensive. Whippets were then assigned to the normal Tank Battalions as extra "X-companies". In an engagement near Cachy, a Whippet company of seven tanks wiped out two German infantry battalions caught in the open, killing over 400. That same day, 24 April, one Whippet was destroyed by a German A7V in the world's second tank battle, the only time a Whippet fought an enemy tank. The Whippet was, a British tank veteran wrote, "the big surprise" of the Royal Tank Corps. Crews used their vehicles' speed to attack troops in the rear. They were so successful that by summer 1918 civilians "seemed to talk in terms of whippets", not knowing of heavy tanks' importance in breaking through fortifications and barbed wire. British losses were so high however that plans to equip five Tank Battalions (Light) with 36 Whippets each had to be abandoned. In the end only the 3rd Tank Brigade had Whippets, 48 in each of its two battalions (3rd and 6th TB). Alongside Mark