Though this plan offered Bonaparte great results, yet in several respects it was somewhat difficult to execute. In order to gain a favorable position for attacking Kray in the Black Forest, Bonaparte would have to make a flank march from Bâle to Lake Constance; and consequently would have to expose his own flank to the attacks of the enemy. But in this case the French flank would be protected by the Rhine; and as Bonaparte would march rapidly, he would in all probability succeed in crossing the river in force near Lake Constance before his adversary should discover his plan. Nevertheless, this flank march would be attended with considerable danger. In fact, every flank march in the vicinity of an active enemy is dangerous; for a commander who gains a position on the enemy's flank must necessarily expose his own flank to the attacks of the enemy. Even when his flank is protected by a river, he cannot cross it without taking some risks. Had Kray's army been assembled in force near Schaffhausen, where it could have attacked the French divisions in detail as they crossed the Rhine, Bonaparte would have had much difficulty in carrying out successfully this plan of campaign. "Of all the operations of war," says Jomini, "there is none more hazardous and difficult than the passage of a large river in the presence of an enemy." Had Bonaparte adopted this plan, he would undoubtedly have attempted to deceive Kray as to the real point of attack. If we form a judgment of what he would have done by what he afterwards did in the Ulm campaign, we can safely assume that he would have ordered at least one division to cross the Rhine from France, and to advance directly eastward upon Kray's army in the Black Forest. The march of this division would have deceived Kray, and would probably have led him to expect the entire French army from that direction. Bonaparte could then have made his flank march in safety, and could have crossed the river with little danger of having his divisions defeated in detail.