To the Green Fields Beyond, Cambrai, France, 20th November 1917 by David Pentland. DHM1538 At 0620 hours covered by a brief barrage from 1000 guns, Brigadier General Elles in a MkIV called Hilda led his 476 tanks against the impregnable German Hindenburg line at Cambrai.  Supported by 6 infantry divisions and 4 Royal Flying Corps squadrons flying ground attack missions, the attack had broken through 3 trench lines and penetrated 5 miles on a 6 mile front by lunchtime.  Although these gains were not exploited and later retaken by a German counter offensive, Cambrai showed the full potential of the tank on the battlefield.