some reason which has never been fully explained but has its justification in psychological factors, suddenly turned and fought a long, severe and straggling battle above Neresheim (August 11). This did not, however, give him much respite, and on the 12th and 13th he retired over the Danube. At this date Wartensleben was about Amberg, almost as far away from the other army as he had been on the Rhine, owing to the necessity of retreating round instead of through the principality of Bayreuth, which was a Prussian possession and could therefore make its neutrality respected. Hitherto Charles had intended to unite his armies on the Danube against Moreau. His later choice of Jourdan's army as the objective of his combination grew out of circumstances and in particular out of the brilliant reconnaissance work of a cavalry brigadier of the Lower Rhine Army, Nauendorff. This general's reports--he was working in the country south and south-east of Nurnberg, Wartensleben being at Amberg--indicated first an advance of Jourdan's army from Forchheim through Nurnberg to the _south_, and induced the archduke, on the 12th, to begin a concentration of his own army towards Ingolstadt. This was a purely defensive measure, but Nauendorff reported on the 13th and 14th that the main columns of the French were swinging away to the east against Wartensleben's front and inner flank, and on the 14th he boldly suggested the idea that decided the campaign. "If your Royal Highness will or can advance 12,000 men against Jourdan's rear, he is lost. We could not have a better opportunity." When this message arrived at headquarters the archduke had already issued orders to the same effect. Lieutenant Field Marshal Count Latour, with 30,000 men, was to keep Moreau occupied--another expedient of the moment, due to the very close pressure of Moreau's advance, and the failure of the attempt to put him out of action at Neresheim. The small remainder of the army, with a few detachments gathered _en route_, in all about 27,000 men, began to recross the Danube on the 14th, and slowly advanced north on a broad front, its leader being now sure that at some point on his line he would encounter the French, whether they were heading for Ratisbon or Amberg. Meanwhile, the Directory had, still acting on the theory of the archduke's weakness, ordered Moreau to combine the operations with those of Bonaparte in Italian Tirol, and Jourdan to turn both flanks of his immediate opponent, and thus to prevent his joining the archduke, as well as his retreat into Bohemia. And curiously enough it was this latter, and not Moreau's move, which suggested to the archduke that his chance had come. The chance was, in fact, one dear to the 18th century general, catching his opponent in the act of executing a manoeuvre. So far from "exterior lines" being fatal to Jourdan, it was not until the French general began to operate against Wartensleben's _inner_ flank that the archduke's opportunity came.