Actual construction was directed by one of Bertrand’s senior battalion commanders and a specialist in bridge building, Colonel Feraudy, known among his peers as the ‘Grand Pontife’. Napoleon, who had now taken up residence in the splendid Schönbrunn Palace south of the city, frequently rode down to visit the site to encourage his officers and men to make even speedier progress. They responded. The main bridge, complete with night illumination and strong railings, was completed by 21 June, as were three additional short pile bridges, each about 25 yards long, connecting the Lobgrund with the Lobau. These were designed for the movement of artillery, ammunition and supplies. Some 50 yards upstream from the main bridge the engineers constructed a second trestle-bridge for the evacuation of the wounded. In addition, during the construction a smaller service bridge, composed of sixty-eight heavy boats and nine substantial rafts, had been placed some 30 yards downstream, and was designated to carry infantry reinforcements only. The ten gunboats, including three captured Austrian craft, armed with small bow howitzers and manned by thirty to fifty sailors each, were assigned to patrol the Danube upstream from the main bridges and were supplemented by another twenty armed river craft. A huge iron chain that the Austrians had employed two centuries earlier to bar the river against the Turks was also sent to Kaiser-Ebersdorf, but proved too heavy and unwieldy and was not used. By working night and day, the French completed the construction of the main trestle-bridge and its subsidiaries – major engineering achievements surpassing the bridges constructed by Caesar and Trajan – in less than a month. Napoleon was justified when he boasted in his 24th Bulletin of 2 July: ‘the Danube no longer exists for the French Army.’
THE LOBAU ISLAND BASE
Even while construction of the bridges proceeded there was much additional activity. On 29 May, Napoleon had already decided on a simultaneous multi-corps assault that would require at least four crossings. In the event there would be ten assault crossings by raft and pontoon bridges, as well as a number of amphibious assault landings, with all necessary matériel prepared on the Lobau. The various small streams and creeks cutting the island were bridged, in some cases widened to that they could conceal the pre-positioned assault barges and bridging equipment until the actual moment of the assaults. Among the assault craft, pontoons, rafts and such, there was one ingenious piece, a special pre-assembled one-piece flexible bridge, made of fourteen captured pontoons in four sections tied together by rope hinges, which was to be used for crossing from the Lobau to the Ile Alexandre. Moored near the south-east end of the Ile Alexandre, it was to be released into the Stadlau branch. The current would unfold the sections and float them downstream. Then, pulled by a boat, they would swing towards the opposite bank where they were anchored. Iron rods would then be slid into iron brackets from one pontoon to the other, creating a solid bridge, more than 100 yards long with a roadbed wide enough for a three-rank column or one line of led horses.
The intended locations for the assault bridges indicated the continued refinement of Napoleon’s battle plan. Frequently scouting in person along the north and north-east shore of the Lobau, dressed in a sergeant’s greatcoat, he had noted that the Austrians were fortifying the line from Aspern to Gross Enzersdorf, but had pulled their main army out of artillery range. But he had no intention of repeating his crossing into the Mühlau, though he planned to deceive the enemy by demonstrations and feints in this area. He planned that the actual crossings would be mounted during the night from the east side of the Lobau through and around the Ile Alexandre in the direction of Gross Enzersdorf. The most southerly attack would protect the flank while in the north the Lobau batteries would provide support. As he pointed out to Berthier, this plan provided an element of surprise, deceiving the Austrians and avoiding a frontal attack against the Austrian fortified line.4 Once across and on the Marchfeld, the army would wheel west and roll up the Austrian left flank along the river.
The Lobau became the advanced fortified base, supply depot and assembly area. There were two main roads on the island. The first led from the Lobgrund to the site of the crossing used on 20 May, the second ended up opposite the Ile Alexandre. A complete network of secondary roads, graded and signposted, gave easy access to all points of the island where magazines, depots, workshops and field hospitals, as well as a large bakery were established. The stores included 300,000 bread rations, 200,000 bottles of wine and 15,000 pints of brandy. By the end of June, 4 Corps was encamped on the Lobau while 2 Corps was assembled around Kaiser-Ebersdorf. To secure the island against an Austrian coup, Napoleon had ordered the construction of small defensive works. A small battery protected the inlet between the Lobgrund and the Lobau in the south-west. On the north-west side, going from west to east, since the end of May the Tabor islands, north of the Leopoldstadt suburb, had been garrisoned by troops from General Friant’s division of Davout’s 3 Corps. Designed to defend Vienna, but perhaps more as a deception, the two islands were each armed with a four-gun 6-pounder battery, while on the Leopoldstadt river bank a battery of four captured 18-pounders was emplaced.
Napoleon intended to use Lobau Island and the various islets in the Danube as concentration areas and forward artillery bases to cover the assault crossings, destroy the Austrian works and guns along the river line and provide fire support during the initial stages of his deployment on the Marchfeld. In their report of 3 June, Generals Foucher and Rogniat had estimated that a minimum of seventy heavy and medium pieces would be needed to support the planned operations. In the event, 124 captured pieces were installed or kept ready in reserve. Emplaced during June and the first three days of July, there were 31 pieces on the north side and 75 on the east side, with a reserve of 18 mobile 12-pounders with some of the batteries positioned on the islands, especially the Ile Alexandre. Napoleon ordered all guns supplied with 300 rounds of ammunition. By type there were 28 heavy 18-pounders, 24 lighter 12-pounders, 17 heavy 28cm-mortars, 10 howitzers and a variety of smaller pieces, mainly 6- and 4-pounders. A carefully worked out fire plan envisaged the elimination of the Austrian fortifications and the demolition of Essling and Gross Enzersdorf. Other designated targets included individual works from Aspern east and south, down to the small Austrian position known as the Maison Blanche, about a mile-and-a-half below the Ile Alexandre. General Aubry, later replaced by Jean-Louis Ebénézer Reynier, was appointed in overall command of the Lobau artillery.5
CONCENTRATING THE ARMY
Napoleon always attached supreme importance to artillery, and had been shaken by the fire of the numerically superior and concentrated Austrian artillery at Aspern–Essling. Therefore he and his director of artillery, General Gaston Lariboisière, who had replaced Songis de Courbons, mortally wounded at Aspern–Essling, took steps to strengthen the artillery assigned to the corps. Immediately after the battle, on 25 May, he ordered Lariboisière to redistribute corps artillery and to issue captured guns to 2, 3 and 4 Corps as well as the Cavalry Reserve. Oudinot’s 2 Corps received an additional forty-eight pieces, while Davout’s 3 Corps and Masséna’s 4 Corps were each allotted sixty-six guns, making these two elite corps the most artillery-heavy in the army.6 The Cavalry Reserve had twenty-six guns. But this was still not enough for the emperor, and more guns were collected from everywhere in his empire. Eugène was instructed to bring as many guns as possible, eventually arriving with 100, some of them pieces captured at various Austrian fortresses and depots. Towards the end of June the emperor was delighted by the arrival of Colonel Antoine Drouot with the bulk of the field artillery of the Guard, including three cherished 12-pounder batteries, bringing the total Guard artillery to sixty pieces. By 4 July, inclusive of the Lobau and island batteries, Napoleon disposed of 617 pieces of artillery and could deploy 488 guns in the field for the next battle.
The emperor was determined to fight this battle with superior numbers and he brought up all possible reinforcements. A substantial number of wounded returned to duty and units were brought up to strength with replacements. All the depots
of the Rhine and Italy were emptied and refilled with 40,000 recruits of the class of 1809. Two strong corps, Masséna’s 4 Corps (21,300 infantry, 6,100 cavalry, 2,800 artillery, 186 guns) and Oudinot’s 2 Corps (26,000 infantry, 1,600 cavalry, 1,900 artillery, 64 guns), were already deployed on the island or near the main bridge. But in order to maintain the element of surprise, the emperor did not concentrate additional large formations until the end of June, and orders to concentrate near Vienna were issued only on 24 June.
At this time Davout’s powerful 3 Corps, which once across the Danube would constitute the right wing of the deployed army and therefore had three cavalry divisions attached, Grouchy, Pully, and Montbrun, shifted from its position downstream at Pressburg towards Vienna. Concentration speeded up during the last week of June as the emperor called in his outlying corps to assemble at Kaiser-Ebersdorf. These included Eugène’s army, which had pushed John’s forces into Hungary, defeated them on 14 June in the battle of Raab and then driven them across the Danube where their positions around Pressburg, including a small bridgehead across the Danube, were to be screened by Severoli’s Italian division. The Army of Italy – two French corps under Generals Macdonald and Grenier, as well as the two mounted brigades of the Royal Italian Guard, a total of 19,000 infantry, 2,000 cavalry, 1,700 artillery and 33 guns – moved towards Vienna. Also ordered to Vienna was Bernadotte’s 9 Saxon Corps, which consisted of two Saxon divisions with the weak French Dupas division attached. In all, Bernadotte had 15,500 infantry, 3,100 cavalry, 900 artillery and 38 guns. Hustling up from Styria, harried by peremptory orders to move his corps, described by the emperor as ‘the most beautiful in my army’, to a faster pace was Marmont’s Army of Dalmatia, the 11 Corps. Though small – only two divisions with 9,700 infantry, 300 cavalry, 700 artillery and 28 guns – almost all its units comprised hardened veterans.7 Assembling east of Vienna was the three-division cavalry reserve under Bessières (8,200 cavalry, 500 artillery, 28 guns). Once reinforced, the Bavarian division under General Wrede, a combined force with 5,400 infantry, 1,100 cavalry, 700 gunners and 24 guns, after marching 125 miles in six days, would arrive late on 4 July. Meanwhile Vandamme’s 8 (Württemberg) Corps (8,600 infantry, 2,200 cavalry, 900 artillery and 40 guns), secured Vienna and guarded the riverbank upstream. Napoleon boasted that he would attack with 180,000 men, but this number included the Lobau garrison, engineers and sappers and his medical staff and other non-combatants. Actually, the emperor disposed of between 150,000 to 175,000 effectives in the coming battle: 260 battalions, 207 squadrons and 617 guns.8
FORMULATING THE ATTACK PLAN
Napoleon’s concentration of his forces was a considerable achievement. It assembled the great bulk of the Army of Germany. Only Vandamme’s Württembergers, positioned along the Danube upstream from Vienna, two divisions of Lefebvre’s Bavarians, detailed to contain the Tyrolean insurrection, and one division of the Army of Italy, detailed to screen Pressburg out of the battle, were left out of the attack. The date for the assault was fixed on 24 June when, instructing Eugène and Davout to arrive at Kaiser-Ebersdorf by 2 July, Napoleon told them that ‘I intend to attack the enemy on the 5th’. Five weeks after having been repulsed and driven back across the Danube, Napoleon had converted the Lobau into an impressive fortified fire base, built three substantial bridges across the Danube and prepared eight assault bridges. In addition, he had procured a Danube flotilla of ten gunboats and other armed craft, as well as five large ferries, each capable of carrying 300 men, and a number of flatboats and barges. He had also had elaborated an overall battle plan. The enemy would be confused by several feints north from the Lobau, while the main thrust would be delivered from its east side. During the night the Stadlau branch would be crossed from the north and south ends of the Ile Alexandre to the Marchfeld plain, with amphibious assaults on the Hanselgrund from the south end of the Lobau to precede this movement. Once across the Stadlau branch, the army would deploy in three battle lines and, rolling up the Austrian positions along the river and pivoting on Gross Enzersdorf, envelop the enemy and destroy him.
THE FINAL PREPARATIONS FOR THE CROSSING
Napoleon was always an improviser and did not believe that it was possible to plan a battle in detail, but he realized that a multi-corps night crossing had to be planned meticulously. As usual, Berthier and his staff worked out the details. To deceive the enemy, on 30 June Napoleon ordered one of Masséna’s divisions, Legrand’s, to cross the Stadlau branch into the Mühlau at the same spot he had crossed in May and establish a bridgehead there. Covered by the fire of thirty-six guns, some 800 infantry made the 100-yard crossing by boat. French engineers then emplaced a short pontoon bridge and by 5 p.m. Legrand had crossed it, pushing back three Austrian battalions and immediately throwing up substantial earthworks and emplacing six artillery pieces.
There was no major Austrian reaction until the next day when Charles moved his main force close to the river. But after being fired on from the Lobau and realizing the threat from the massive French batteries, the next day he pulled his men back to their original positions on the line of the Russbach to the Bisamberg. During the following night Napoleon moved his headquarters to the south-west part of the Lobau, where he was joined by the Imperial Guard. As a further deception, four additional bridges were built from the north shore of the Lobau to the opposite bank, and on 2 July a small feint was undertaken towards Stadlau, upriver from Aspern. On this occasion French guns bombarded the Austrian positions, 500 men landed on the Schierling Grund, while further east Masséna was directed to seize the Ile Bessières just below the Mühlau and place an eight-gun battery there to dominate the river bank up to Gross Enzersdorf. The same day, heavy batteries on the Lobau again opened fire on Austrian works and troops near Gross Enzersdorf, inflicting heavy damage and 300 casualties. Archduke Charles, who had advanced II and III Corps close to the river line, now pulled his main forces back and issued orders that they were not to support the units of the Advance Guard and VI Corps holding the river line without his direct orders.
Napoleon prepared and issued final movement orders between 2 and 4 July. His plan was based on deception, the demonstrated slow reaction of the Austrians and sheer weight of numbers and firepower. Late on 2 July, Berthier issued Napoleon’s instructions regarding the placement of the formations on the Lobau and the order and timing of their crossing to the left bank. As far as possible they were to bivouac close to their designated crossings and in the order of battle they were to assume once across the river. During the day the bridges, policed by gendarmes of the Imperial Guard, were reserved for transport of stores; troop movement was to be under the cover of darkness. The first line of battle was to consist of 4, 2, and 3 Corps with attached cavalry. Masséna’s 4 Corps, still minus Legrand’s division, deployed on the north-east side of the Lobau, and Oudinot’s 2 Corps crossed soon after darkness on the night of the 3rd to take up positions in the south-east. The Imperial Guard, 7,400 infantry, 3,400 cavalry, 1,600 artillery and 60 guns, followed at 8.30 p.m. Finally at 11 p.m. 9 Corps, which was to assemble on the north-west of the island to convey the impression of an attack north, crossed into the Lobau. The movement of stores occupied most of the daylight hours of 4 July, but after dark Davout was to cross, taking his station slightly to the rear between Masséna and Oudinot.
The second line was to be formed of the Army of Italy, two French divisions and the Royal Italian Guard, crossing at 1 a.m. on the 5th to deploy on the left, followed before dawn by Bernadotte’s corps taking up positions on the right. The Imperial Guard, already encamped on the Lobau, would occupy the centre, while the light cavalry was to cross at 3.00 a.m. followed by the Reserve Cavalry, three heavy divisions under Bessières. Marmont’s corps and the Bavarians were not expected until late on 5 July and were to act as reserves on the second day.
Also on 2 July, specific fire plans were issued for the Lobau and the batteries on the adjoining islands. Here General Reynier was to take command at noon on 4 July. In addition t
o the gunners and such, he was to have a number of detached infantry units: one Baden regiment from Masséna, two battalions from Oudinot, two battalions of Saxons from Bernadotte as well as Berthier’s Neuchâtel battalion. The various units were to defend the batteries on and around the Lobau while the Neuchâtel battalion, Berthier’s own, was to replace Legrand’s division in the Mühlau bridgehead during the night of 4–5 July. The timing of the first amphibious assaults, the placing of the assault bridges and the order of march for correct deployment on the other side were crucial. That close-on 150,000 men with their horses, guns and ammunition trains were able to cross the river in a single night was a triumph of staff work. There was only a minor mix-up, between elements of Davout’s and Oudinot’s corps when, because of an oversight by Berthier’s staff, Davout crossed by the centre instead of the right bridge, causing each corps to cross the other’s line of march during the night.
A complication had threatened on 2 July when Masséna was incapacitated after being thrown from his horse, but much to Napoleon’s delight the marshal refused to stand down and told the emperor that he would utilize his light carriage. ‘With you on my left flank,’ the emperor remarked, ‘I feel assured’. Though in considerable pain, Masséna conducted his corps during the days of battle by riding in a phaeton drawn by four white horses and handled by two elaborately uniformed civilian coachmen. If his visibility encouraged his own troops, it also made him a clear target for the Austrian gunners. Indeed one horse was killed during the second day, but Masséna remained unscathed. In vivid contrast to Masséna, on the Austrian side, General Hiller, commanding VI Corps, was so unhappy with his dispositions – ‘I repeatedly have warned that the fortifications are too weak’, he complained – that on 4 July he asked for and received permission to leave the army on the grounds of ill health.
The Emperor's Last Victory Page 13