The same reason makes it probable that the passage of the river at Schaffhausen, the most difficult problem of Bonaparte's plan of campaign, might have been accomplished before Kray learned the designs of his adversary. Another fact confirms this view. It will be remembered that, after Moreau crossed the Rhine with his four corps, twenty-six thousand French soldiers still remained in Switzerland and in the French fortresses along the Rhine. Inasmuch as a part of this force was occupying Strasburg, it is quite probable that, had Bonaparte's plan been adopted, a division of four or five thousand men would have issued from the bridge-head opposite this place, and have attacked the Austrians on the west side of the Black Forest. Such an attack would probably have deceived Kray, and have left him in doubt as to where the French intended to cross the river in force; it would probably have caused him to leave Kienmayer's corps in its position, and have prevented him from uniting a sufficient force in the vicinity of Schaffhausen to oppose the passage of the French. It will be remembered that Bonaparte had already made some preparations for crossing the Rhine near Schaffhausen; he had secretly collected a number of boats on the river between Bâle and Lake Constance. These boats were to be used for the crossing of the advance divisions. The purpose also was to throw two or three bridges across the river; the material for which could have been collected and prepared by Lecourbe's corps while the remaining corps were ascending the Rhine. It will also be noticed that the point selected by Bonaparte for the crossing was a favorable one. During the passage Lake Constance would have protected the right flank of the French corps from an Austrian attack, and would have continued to protect them as they marched towards Stokach. Though the crossing of a large river in the face of an active enemy is a difficult operation, yet it is generally successful, because great pains is nearly always taken to deceive the enemy, and because great preparations are nearly always made to insure the success of the operation. "If," says Jomini, "we take into consideration the great care and precautions that are requisite, the immense amount of materials employed in such an operation, the concurrence of circumstances necessary to secure success, and the difficulties which may be occasioned by the slightest derangement on the part of the enemy, it is really surprising that an operation of this kind ever succeeds. Nevertheless, wonderful as it may seem, the most difficult military enterprises are commonly the most successful, from the simple fact that greater care and precautions are employed in their execution."