The Campaign of Marengo, With Comments

by Herbert H. Sargent

The most critical part of Bonaparte's operations was the flank march from Ivrea to Milan; for at this time his only line of retreat was by way of the Great St. Bernard; and even on this route the Austrians still held Fort Bard.

Under ordinary circumstances, a flank march is always more or less a hazardous undertaking. When a commander makes this movement and is attacked in route, he must form front to a flank,[10] and fight with his battle-line parallel to his communications, while the enemy can fight with his front perpendicular to his communications. In this position the advantage of the enemy is enormous. If victorious, he severs the communications of his adversary, and may then capture or destroy his army; if defeated, he can retreat in safety along his communications, or fall back to a new position, fight again, and thus prolong the conflict. An army without communications is like a rudderless ship adrift on the ocean. In order to fight, soldiers must have food and ammunition. No greater calamity, short of defeat, can befall a commander than to be cut from his base of operations and lose his source of supply.

Had, therefore, the Army of Reserve been defeated while marching from Ivrea to Milan, it would have lost its line of communication by way of the Great St. Bernard. In that case it would undoubtedly have been captured or destroyed; for since the Italian entrances of the St. Gothard and Simplon passes were then held by ten thousand Austrians under Vukassovich, Bonaparte could not have retreated into Switzerland.

That Bonaparte appreciated the critical features of the situation is seen in the skill with which he planned and executed the march. By ordering Lannes to make preparations to cross the Po at Chivasso, Bonaparte gave Melas the impression that the French intended to cross the Po and attack the Austrians near Turin. Thus Melas was deceived. Meanwhile Bonaparte, with the greater part of the Army of Reserve, marched rapidly on Milan. During the march Lannes descended the Po towards Pavia, thus covering as with a screen the movements of Bonaparte. So skilfully were these manœuvres made that Melas did not even attempt to cross the river, in fact, did not even learn of the march of Bonaparte until the 29th of May, two days after the movement had begun. On the 31st Bonaparte arrived on the Ticino; and on the 2d of June, having driven back Vukassovich's corps, he entered Milan. Here the critical part of his march ended, for he was then sure of being joined by Moncey's corps, and had, in case of need, a safe line of retreat into Switzerland by the St. Gothard and Simplon passes.

Another circumstance that aided Bonaparte in this march was the presence of Thurreau's division of four thousand men at Susa. Melas, being ignorant of the strength of this division, hesitated to push forward and attack Lannes, so long as these troops remained undefeated on his flank and rear. On this point General Hamley makes the following comments:—

"Thurreau's force, being entirely separated from the main army throughout the operations, was useful only as leading the enemy to a false conclusion. But its value in that respect was incalculable. There were sufficient Austrian troops round Turin to check Thurreau and crush Lannes, thus laying bare the rear of the French army. But the road of the Mont Cenis was both more practicable and more direct than that of the St. Bernard; moreover, Thurreau had artillery, and Lannes, at first, had not, for his guns had been delayed by the difficulties of passing the Austrian fort of Bard. It was but a natural error, therefore, for Melas to believe that Thurreau was backed by the whole French army."

Upon his arrival at Milan a threefold problem confronted Bonaparte. His object was to prevent the escape of the Austrians, to preserve his communications with Switzerland, and, in case of an Austrian attack, to make a quick concentration for battle. The skill with which he solved this complex problem will become apparent, if we turn to the map and study the positions of the French forces immediately after the arrival of Moncey's corps. These forces numbered fifty-five thousand men. Thirty-two thousand were stationed along the Po from Placentia to the Stradella Pass on the great highway leading from Alessandria to Mantua; ten thousand were stationed on the Ticino; ten thousand on the Adda; and three thousand at Milan. Thus it will be seen that these forces were occupying the sides of the triangular space enclosed by the Ticino, the Po, and the Adda; and that they held possession of all the roads leading from the Alps to the Austrian base of operations on the Mincio. The ten thousand men on the Ticino not only protected the Italian entrance to the St. Gothard on the west side, but they were in a position to dispute the passage of the Ticino, should Melas cross to the north side of the Po and attempt to reach Mantua by way of Pavia and Milan. In the event that Melas should adopt this plan, the resistance that these ten thousand men could offer him would give Bonaparte time to unite all his forces for battle on the north side of the Po. The thirty-two thousand men on the south side of the Po closed with a barrier of steel the great highway leading from Alessandria to Mantua. On this road they had fortified a camp at the Stradella; and across the Po they had constructed five bridges, which would enable Bonaparte, in an emergency, to recross the river rapidly with these troops. The ten thousand men along the Adda not only covered the Italian entrance to the St. Gothard on the east side, but they were in a favorable position for holding in check Vukassovich's corps, should it attempt to march westward to the relief of Melas. It will be observed, too, that, should Melas attempt to escape by marching to Genoa, and thence to Mantua by way of Bobbio and Placentia, the French forces about Placentia and along the Adda could delay the progress of the Austrians long enough for Bonaparte to concentrate all his forces against them.

Occupying a triangle in the heart of northern Italy, the French corps and divisions supported one another. In a few hours Bonaparte could concentrate nearly the whole of his army on the Po, on the Ticino, or on the Adda. In this position he held complete possession of the Austrian communications, and had his own with Switzerland strongly guarded. In this position he could concentrate quickly, and fight with nearly every advantage in his favor.

"Napoleon has told us," says Colonel Hart, "that the whole art of war—the secret of success—consists in being strongest at the decisive point." Even when making a great flank or turning movement against his enemy, Napoleon kept this principle constantly in view. Thus, in these operations, though at the outset the several columns under his immediate command, numbering nearly sixty thousand men, entered Italy from different directions, separated by intervening obstacles and great distances, yet, by deceiving his adversary and by skilful manœuvres, he succeeded in conducting fifty-five thousand men into such positions that they could, in an emergency, support one another on a single battle-field. His theory of war was concentration. His constant endeavor was to outnumber the enemy in battle. In order to accomplish this result, he nearly always made a great effort to call in his detachments just previous to a general engagement. His skill in strategy consisted in so directing his columns that when needed they could be quickly assembled on the battle-field. His skill in war consisted in the fact that he nearly always brought greater numbers against his enemy on the day of battle, even when he was outnumbered within the theatre of operations. On the battle-field, too, when it was impossible to outnumber his adversary, his quick eye discerned the vital point, the key of the position, so to speak; and there, neglecting the less important points, he massed his troops and overwhelmed his enemy. But in this campaign, strange to relate, after the battle of Montebello, and prior to the battle of Marengo, he seemed to neglect the principle of calling in his columns. When he assembled his forces south of the Po in the Stradella Pass, he felt certain that Melas would shortly advance eastward from Alessandria to attack him; yet he issued no orders for his forces north of the Po to join him. Again: at Marengo he was outnumbered, while ten thousand French soldiers along the Ticino, but a short distance away, had not a single Austrian in their front.