This handicap may be stated by a consideration of three points which cover its whole character.
The first of these points concerns the physical conditions of the move; the other two are peculiar to the political differences of the allies.
It was in the nature of the move that a high hazard was involved in it. The general had calculated, as a general always must, the psychology of his opponent. If he were wrong in his calculation, the advance on the Danube could but lead to disaster. It was for him to judge whether the French were so nervous about the centre of their position upon the Rhine as to make them cling to it to the last moment, and tend to believe that it was either along the Moselle or (when he had left that behind) in Alsace that he intended to attack. In other words, it was for him to make the French a little too late in changing their dispositions, a little too late in discovering what his real plan was, and therefore a little too late in massing larger reinforcements upon the Upper Danube, where he designed to be before them.
Marlborough guessed his opponent’s psychology rightly; the French marshals hesitated just too long, their necessity of communicating with Louis at Versailles further delayed them, and the great hazard which he risked was therefore risked with judgment. But a hazard it remained until almost the last days of its fruition. The march must be rapid; it involved a thousand details, each requiring his supervision and his exact calculation, his knowledge of what could be expected of his troops, and his survey of daily supply.
There was another element of hazard.
Arrived at his destination upon the plains of the Danube, Marlborough would be very far from any good base of supply.
The country lying in the triangle between the Upper Danube and the Middle Rhine, especially that part of it which is within striking distance of the Danube, is mountainous and ill provided with those large towns, that mobilisable wealth, and those stores of vehicles, munitions, food, and remounts which are the indispensable sustenance of an army.
The industry of modern Germany has largely transformed this area, but even to-day it is one in which good depots would be rare to find. Two hundred years ago, the tangle of hills was far more deserted and far worse provided.
By the time Marlborough should have effected his junction with his ally in the upper valley of the Danube only two bases of supply would be within any useful distance of the new and distant place to which he was transferring his great force.
The most important of these, his chief base, and his only principal store of munitions and every other requisite, was Nuremberg; and that town was a good week from the plains upon the bank of the Danube where he proposed to act. As an advanced base nearer to the river, he could only count upon the lesser town of Nordlingen.