"Tanks were first used by the British on the 15th September, 1916, in the Battle of the Ancre. They had, however, been designed to meet the conditions which existed _in the preceding year_, before the tremendous artillery bombardments of the middle stages of the war reduced the ground to a series of shell-holes and craters, which were so closely continuous over a large area of ground that they could not possibly be avoided. Compared with the latest type of tank, our first effort--known as Mark I.--may appear crude; but much genius had been expended upon it, and it is worth noting that both the French and German tanks, produced long after this tank, were much inferior to it. "The Ypres salient, let me begin by saying, was never favourable to the employment of tanks. In the Third Battle of Ypres (31st July to November, 1917), which I personally believe to have been the hardest battle of the whole war, the tanks were unable to cope with the wet and shelled ground." Nevertheless, towards the end of the Ypres battle the tank attack in the first Battle of Cambrai was being planned, and there, at last, the enthusiasts of the Tank Corps had the conditions for which they had been long hoping--a good ground and a surprise attack. "It is important to remember, the letter continues, that the Hindenburg line at that time presented an insoluble problem. The _sea of wire_ which protected its well-developed trenches and machine-gun positions was placed almost throughout on the _reverse slope_ of the hills or rising ground of which the line took advantage. The artillery observer could hardly get a view of the wire at all; beside which, it was so deep it would have taken a month to cut it by artillery fire. "_The tank provided the solution_--the only solution. The tank, by _crushing down the wire_--in a few minutes--was able to do what there seemed no other way of doing. And the tank success at Cambrai was not a mere flash in the pan. To the end of the war the Hindenburg line, or any other line organised in the same way, was entirely at the mercy of the tanks. "The tanks, however, did not make their full weight felt until August, 1918. They had become a very important factor before that, and had saved thousands of lives; but from the beginning of the counter-offensive of last year they were a dominating feature of the war. Ludendorff had already recognised their importance in July, after the French use of them in the Battle of Soissons, when he wrote to his Army Commanders that 'the utmost attention must be paid to combating tanks. Our earlier successes against tanks led to a certain contempt for this weapon of warfare. We must now reckon with more dangerous tanks.'"