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 IV and V tanks, they took part in the Amiens offensive (8 August 1918) which was described by the German supreme commander General Ludendorff, as "the Black Day of the German Army". The Whippets broke through into the German rear areas causing the loss of the artillery in an entire front sector, a devastating blow from which the Germans were unable to recover. During this battle, one Whippet – "Musical Box" – advanced so far it was cut off behind German lines. For nine hours it roamed at will, destroying an artillery battery, an observation balloon, the camp of an infantry battalion, and a transport column of the German 225th Division, inflicting heavy casualties. At one point, cans of petrol being carried on "Musical Box"'s roof were ruptured by small-arms fire and fuel leaked into the cabin. The crew had to wear gas masks to survive the fumes. Eventually, a German shell disabled it and as the crew abandoned the tank, one of them was shot and killed, and the other two were taken prisoner.