Meanwhile the detachment under Bethencourt, marching by way of the Simplon Pass, had reached Arona at the lower end of Lake Maggiore. On the 1st of June Fort Bard surrendered to Chabran. Having left a garrison in this place, and one also in Ivrea, he then took up a position with the remainder of his corps along the Po from Chivasso to the Sesia River. From the Sesia to Pavia the corps of Lannes occupied the line of the Po. On the 1st of June Lannes had captured this place, and had seized the large magazines there, which contained provisions, several pieces of artillery, and a number of pontoon boats.
Thus it will be seen that the French were in possession of the whole of northern Italy lying between the Po and Switzerland. Looking south from Milan, Bonaparte had in his front the line of the Po, which he held from Chivasso to Cremona. Far away to his right was the Great St. Bernard Pass, which he had just crossed, and which was now guarded by the French garrisons of Fort Bard and Ivrea. To his left, at a distance of eighty miles, was the Mincio, which formed on that side the dividing line between the French and the Austrians; and in his rear were the St. Gothard and Simplon passes, which offered him a safe retreat into Switzerland in case he should meet with a reverse. Already, within this territory, he had seized all the Austrian communications, captured several Austrian garrisons, occupied several cities, and taken possession of immense quantities of provisions and munitions of war.
Thus situated, Bonaparte was almost ready to strike the blow that should decide the fate of Italy. In a few days he would cross the Po, march through the Stradella Pass, and encounter Melas on the bloody field of Marengo. The delay at Milan was but the lull before the storm. While Bonaparte remained there, completing his arrangements and awaiting the arrival of Moncey, Melas was beginning to appreciate the situation, and, though still somewhat confused and undecided, was destined shortly to make an heroic effort to save his army.
For several days after Melas reached Turin, he remained in doubt as to the intentions of Bonaparte. In fact, he was deceived by the preparations that Lannes had made to cross the Po at Chivasso. Again: in descending the river towards Pavia, Lannes so masked the main part of the Army of Reserve, that Melas did not immediately become aware of the movement on Milan. But on the 29th of May he learned that Bonaparte was marching on Milan; and, on the 31st, he learned that Moreau had defeated Kray, and that Moncey's corps was marching by way of the St. Gothard into Italy. At once he comprehended the vast plan of Bonaparte. He saw that nothing could now prevent the Army of Reserve from uniting with Moncey's corps; and that, with these combined forces, Bonaparte would doubtless march south from Milan, cross the Po, and sever the Austrian communications. Thus he saw himself being rapidly enclosed in a net from which there would soon be little or no hope of escape. Being now completely undeceived as to the intentions of Bonaparte, Melas had no further cause for delay. He must concentrate his troops at once, in order to break through the French forces rapidly closing in upon him. He must, if possible, preserve his communications, and thus save his army from capture or annihilation.
Accordingly, he determined to concentrate at Placentia and the Stradella Pass all the available Austrian troops that were fighting the French near Genoa. By this means he hoped to seize and hold the crossings of the Po from Pavia to Cremona, and thus to retain possession of the great highway leading from Alessandria through the Stradella Pass to Mantua. He also determined to unite at Alessandria all the available Austrian troops in Piedmont and along the Var. By this means he expected to assemble there an army of at least thirty thousand men, and thence to proceed eastward through the Stradella Pass to Mantua. By following this plan, he hoped to make his escape with the greater part of his army. Having once reached the Mincio, he could unite his forces with those of Vukassovich; and, perhaps, in this strong position, flanked on one side by Lake Garda, and on the other by the fortress of Mantua, he might be able to make a successful stand against Bonaparte.
In accordance with this plan, he sent imperative orders to General Elsnitz to quit the Var and march on Alessandria, and to General Ott to raise the siege of Genoa and hasten north in order to seize Placentia and the crossings of the Po near that point. Meanwhile he himself, having left a sufficient force to hold Thurreau in check, hastened with the remainder of his army to march on Alessandria.
Upon receiving the orders of Melas, General Elsnitz, whose command then numbered but seventeen thousand, began to withdraw his forces from the Var. He directed his columns towards the Tenda Pass, expecting to cross the Apennines at that point, and thence to march on Alessandria by way of Coni, Alba, and Asti. But Suchet, being well aware of the desperate situation of Melas, was anticipating the recall of Elsnitz and was prepared for it. Suchet's forces numbered fourteen thousand men. By skilful manœuvring and by a rapid march across the foothills of the Apennines, he succeeded in reaching the Tenda Pass ahead of his adversary. Having thus turned the flank of the Austrians, and obtained possession of their line of retreat, he fell upon them, defeated them, cut them in two, and killed, wounded, or captured more than half of their army. As a result General Elsnitz was compelled to retreat eastward and cross the Apennines over the Ormea Pass. With only eight thousand men he arrived at Ceva on the 7th of June en route to Alessandria. Meanwhile Suchet, having proceeded eastward to Savona, was joined by a part of Masséna's command, which had marched out of Genoa on the 5th of June. With these combined forces, Suchet marched to Acqui, and there, still acting under the orders of Masséna, awaited the results of Bonaparte's operations.
When, on the 2d of June, General Ott received the orders of Melas, the negotiations for the capitulation of Genoa were pending. He delayed until the 4th of June to receive the surrender of Masséna. On the 6th, having left a sufficient force to garrison the city, he sent a brigade towards Placentia by way of Bobbio; and with the remainder of his forces, numbering sixteen thousand soldiers, he himself marched towards the same place by way of Novi, Tortona, and the Stradella Pass.
During these operations, Bonaparte remained at Milan, perfecting his arrangements and issuing the orders for the movements of his troops. He had already sent forward Berthier to direct the operations along the Po. On the 6th of June Moncey's corps arrived. This re-enforcement of fifteen thousand men increased the effective forces under the immediate command of Bonaparte to about sixty thousand. Immediately upon the arrival of Moncey, thirty-two thousand soldiers under Lannes, Victor, and Murat, began to cross the Po. The remainder of the army were thus stationed: four thousand, under Thurreau, were at the foot of the Mont Cenis Pass; two small detachments were occupying Fort Bard and Ivrea; ten thousand were posted at Vercelli and along the Ticino from the foot of Lake Maggiore to Pavia; three thousand were at Milan; and ten thousand were along the Adda, and at Cremona and Placentia. All these troops, except the division of Thurreau, which was isolated and held in check by an Austrian force near Turin, were available for the operations about Milan and along the Po.
On the 6th of June Lannes and Victor crossed the Po near Belgiojoso, a few miles below Pavia, and marched thence to the Stradella Pass. On the following day Murat crossed at Placentia. In these passages the French met with considerable opposition from small detachments of cavalry and infantry that Melas had directed thither from Alessandria and elsewhere to hold the crossings of the Po until General Ott should arrive; but these detachments having been defeated and driven back, the French occupied Placentia and the Stradella Pass. At the latter place a fortified camp was constructed, and between Pavia and Placentia five bridges were built for the use of the French in case they should be forced to retreat.