Their soil is clay, and though the height of the hills is only three hundred feet above the plain, their escarpment or steep side is towards the east, whence an invasion may be expected. They are densely wooded, from five to eight miles broad, the supply of water in them is bad, in many parts undrinkable; habitation with its provision for armies and roads extremely rare. It is necessary to insist upon all these details because the greater part of civilian readers find it difficult to understand how formidable an obstacle so comparatively unimportant a feature in the landscape may be to an army upon the march. It was quite impossible for the guns, the wagons, and therefore the food and the ammunition of the invading army, to pass through the forest over the drenched clay land of that wet autumn save where proper roads existed. These were only to be found wherever a sort of natural pass negotiated the range.
Three of these passes alone existed, and to this day there is very little choice in the crossing of these hills. The accompanying sketch will explain their disposition. Through the southernmost went the great high road from the frontier and Verdun to Paris. At the middle one (which is called the Gap of Grandpré) Dumouriez was waiting with his incongruous army. The third and northern one was also held, but less strongly. The obvious march for an unimpeded invader would have been from Verdun along the high road, through the southern pass at “Les
