The government of Vienna no sooner heard of this new aggrandisement, than it commenced warlike preparations, rashly and precipitately, without making sure of the co-operation of Berlin, or even waiting until the troops of Russia could perform the march into Germany. But this great fault was not the greatest. The Emperor haughtily demanded that the Elector of Bavaria should take the field also; nay, that he should suffer his army to be entirely incorporated with the Austrian, and commanded by its chiefs. The Elector, who had a son travelling in France, resisted anxiously and strenuously. "On my knees," he wrote to the Emperor, "I beg of you that I may be permitted to remain neutral." This appeal was disregarded. The Austrian troops advanced into Bavaria, where they appear to have conducted themselves as in an enemy's country; and the indignant Elector withdrew his army into Franconia, where he expected the advance of the French as liberators.

This unjustifiable behaviour was destined to be severely punished. No sooner did Napoleon understand that war was inevitable, than he broke up his great army on the coast opposite to England, and directed its march upon the German frontier; while Massena received orders to assume, also, the offensive in Italy, and force his way, if possible, into the hereditary states of Austria. The favourite scheme of Carnot was thus revived, and two French armies, one crossing the Rhine, and the other pushing through the Tyrolese, looked forward to a junction before the walls of Vienna.

The rashness which had characterised the conduct of the Cabinet of Vienna, was fatally followed out in that of its general, Mack: instead of occupying the line of the river Inn, which, extending from the Tyrol to the Danube at Passau, affords a strong defence to the Austrian territory, and on which he might have expected, in comparative safety, the arrival of the Russians—this unworthy favourite of the Emperor left the Inn behind him, and established his headquarters on the western frontier of Bavaria, at Ulm.

Napoleon hastened to profit by this unpardonable error. Bernadotte advanced from Hanover, with the troops which had occupied that electorate, towards Wurtzburg, where the Bavarian army lay ready to join its strength to his; five divisions of the great force lately assembled on the coasts of Normandy, under the orders of Davoust, Ney, Soult, Marmont, and Vandamme, crossed the Rhine at different points, all to the northward of Mack's position; while a sixth, under Murat, passing at Kehl, manoeuvred in such a manner as to withdraw the Austrian's attention from these movements, and to strengthen him in his belief that Napoleon and all his army were coming against him through the Black Forest in his front.

The consequence of Buonaparte's combinations was, that while Mack lay expecting to be assaulted in front of Ulm, the great body of the French army advanced into the heart of Germany, by the left side of the Danube, and then, throwing themselves across that river, took ground in his rear, interrupting his communication with Vienna, and isolating him. In order that Bernadotte and the Bavarians might have a part in this great manœuvre, it was necessary that they should disregard the neutrality of the Prussian territories of Anspach and Bareuth; and Napoleon, well aware of the real sentiments of the court of Berlin, did not hesitate to adopt this course. Prussia remonstrated indignantly, but still held back from proclaiming war; and Napoleon cared little for such impediments as mere diplomacy could throw in the way of his campaign. He did not, however, effect his purpose of taking up a position in the rear of Mack without resistance. On the contrary, at various places, at Wertenghen, Guntzburg, Memingen, and Elchingen, severe skirmishes occurred with different divisions of the Austrian army, in all of which the French had the advantage. General Spangenburg and 5000 men laid down their arms at Memingen; and, in all, not less than 20,000 prisoners fell into the hands of the French between the 26th of September, when they crossed the Rhine, and the 13th of October, when they were in full possession of Bavaria and Swabia, holding Mack cooped up behind them in Ulm—as Wurmser had been in Mantua, during the campaign of Alvinzi.

But Mack was no Wurmser. Napoleon's recent movements had perplexed utterly the counsels of the Austrians, whose generals, adopting different views of the state of the campaign, no longer acted in unison. Schwartzenberg, and the Archduke Ferdinand, considering further resistance in Bavaria as hopeless, cut their way, at the head of large bodies of cavalry, into Bohemia, and began to rouse the inhabitants of that kingdom to a levy en masse. The French Emperor, perceiving that they had for the present escaped him, drew back upon Ulm, invested that town on every side, and summoned Mack to surrender.

The garrison consisted of full 20,000 good troops; the place was amply victualled and stored; the advance of the great Russian army could not be distant; the declaration of war against Napoleon by Berlin was hourly to be expected: and the armies of Austria, though scattered for the present, would be sure to rally and make every effort for the relief of Ulm. Under circumstances comparatively hopeless the brave Wurmser held Mantua to extremity. But in spite of example or argument, in terror or in treachery, General Mack capitulated without hazarding a blow.

On the 16th he published a proclamation, urging his troops to prepare for the utmost pertinacity of defence, and forbidding, on pain of death, the very word surrender to be breathed within the walls of Ulm. On the 17th he signed articles by which hostilities were immediately to cease, and he and all his men to surrender themselves prisoners of war within ten days, unless some Austrian or Russian force should appear in the interval, and attempt to raise the blockade. After signing this document, Mack visited, in person, the headquarters of Napoleon; and, whatever the nature of their conversation may have been, the result was, a revision of the treaty on the 19th, and the formal evacuation of Ulm on the 20th. Twenty thousand soldiers filed off, and laid down their arms before Napoleon and his staff.—Eighteen generals were dismissed on parole; an immense quantity of ammunition of all sorts fell into the hands of the victor; and a waggon filled with Austrian standards was sent to gratify the vanity of the Parisians.

The catastrophe of Ulm, striking new terror into the Prussian counsels, prevented the violation of the territory of Anspach from being immediately followed by the declaration of war, for which Buonaparte must have made up his mind when he hazarded that measure. Meantime success had attended Massena in his advance from Lombardy towards the Venetian states, where the Archduke Charles commanded an army of 60,000 men for Austria. The Archduke, after sustaining various reverses, was forced to abandon Italy; and retreated, though slowly and leisurely, before Massena, through the strong passes of the Carinthian mountains.

Nor had Marshal Ney, whom Napoleon had detached from his own main army with orders to advance in the Tyrol, been less successful than Massena. The Archduke John, who commanded in that province, was beaten like his brother; and the outposts of the army of Massena from Italy and that of Ney from the Upper Rhine, at length met and saluted in triumph at Clagenfurt. The Archduke Charles, understanding how Ney was prospering in the Tyrol, had given up the design of retreating by that way into Germany, and proceeded through the Carinthian Mountains towards Hungary. Prince John now followed his brother's example; and, the remains of those two armies thus coalescing in a distant region, the divisions of Ney and Messena came to be at the immediate disposal of Napoleon, who was now concentrating his force for the purpose of attacking Vienna.