In the Battle of Aspern–Essling (21–22 May 1809), Napoleon crossed the Danube near Vienna, but the French and their allies were attacked and forced back across the river by the Austrians under Archduke Charles. It was the first time Napoleon had been personally defeated in a major battle, as well as his first battle defeat in 10 years since the siege of Acre, and his first battle defeat as head of state, although he did suffer a tactical defeat in the Battle of Caldiero and in the Second Battle of Bassano. Archduke Charles drove out the French but fell short of destroying their army. The French lost approximately 23,000 men, including one of Napoleon's ablest field commanders and closest friends, Marshal Jean Lannes.
Background
On 10 April 1809, Austrian troops under Archduke Charles had crossed the border into Bavaria, a French client state; thus beginning hostilities without a declaration of war. The French, initially taken by surprise, were able to defeat the Austrians at Eckmühl, Abensberg and Ratisbon. The Archduke, fearing that his army might be destroyed, retreated towards Bohemia. After these victories the way to Vienna for Napoleon was eventually open. By 13 May Napoleon had entered the City.
Prelude
Considering the French army would need to rest at Vienna, Charles decided to march there, joining Hiller at the Marchfeld. When he arrived there, he had an army of 115,000 men at his disposal. Napoleon could muster only 82,000 troops. The 8th and 9th Corps, numbering 38,000, were back on the River Traun, observing Johann Kollowrath's 25,000 Austrian troops who were entrenched on the north bank of the Danube near Linz. At the same time, they were safeguarding Napoleon's communications with France and his current centre of operations. They were also dealing with the inconvenience posed by local risings, which were becoming a constant source of concern. Davout, having previously crossed his corps to the south bank of the Danube via Straubing and Enns, was engaged on similar duties with 35,000 men near St. Polten on the River Traisen, approximately 40 miles west of Vienna. Meanwhile, Lefebvre's 7th Corps, comprising 22,000 personnel, was engaged in monitoring the movements of Archduke John's forces, specifically 8,000 troops stationed in Innsbruck and 7,000 more under Jellacic on the higher reaches of the River Enns, from the vicinity of Salzburg. In addition, the remaining 30,000 Austrians of Archduke John's army was responsible for maintaining a watch on the 57,000 Frenchmen of Eugene’s Army of Italy in Carinthia and Carniola.
Francis urged the Archduke to take immediate offensive action, given numerical superiority, but Charles had no wish to venture a major attack across the Danube. Charles argued that, by remaining on the left bank of the river, the army would retained freedom of manoeuvre. Napoleon wanted an early battle and he was aware that a decision was required urgently. He was concerned about the potential for unrest in his rear, the approach of John's army and the possibility of Prussian intervention and a reversal of Russia's position. Furthermore, he held the Austrians in low regard and believed that the main army was retreating into Moravia. He did not believe that it was in a position to deliver a significant battle on the northern bank of the Danube.
The French wanted to cross the Danube. A first crossing attempt on the Schwarze Lackenau was repulsed with some 700 French losses. Lobau, one of the numerous islands that divided the river into minor channels, was selected as the next point of crossing. Careful preparations were made and on the night of 19–20 May the French bridged all the channels on the right bank to Lobau and occupied the island. By the evening of the 20th many men had been collected there and the last arm of the Danube, between Lobau and the left bank, had been bridged. Masséna's corps at once crossed to the left bank and dislodged the Austrian outposts. Undeterred by the news of heavy attacks on his rear from Tyrol and from Bohemia, Napoleon ferried all available troops to the bridges, and by daybreak on the 21st, 25,000 men in three infantry and two cavalry divisions were collected on the Marchfeld, the broad plain of the left bank which was also to be the scene of the Battle of Wagram.
Charles did not resist the passage. It was his intention as soon as a large enough force had crossed to attack it before the rest of the French army could come to its assistance. Napoleon had accepted the risk of such an attack but he sought at the same time to minimize it by summoning every available battalion to the scene. His forces on the Marchfeld were drawn up in front of the bridges facing north with their left flank in the village of Aspern (Gross-Aspern) and their right in Essling. Both places lay close to the Danube and could not therefore be turned; Aspern, indeed, is actually on the bank of one of the river channels. The French had to fill the gap between the villages and also move forward to give room for the supporting units to form up.
Order of battle
Austrian
Kaiserlich-Königliche Hauptarmee, under the command of Charles of Austria:
Total: 99,000 men (84,000 infantry, 14,250 cavalry), 288 guns
The corps led by Johann von Hiller (VI), Heinrich Graf von Bellegarde (I) and Prince Friedrich of Hohenzollern-Hechingen (II) were to converge upon Aspern, while Prince Franz Seraph of Rosenberg-Orsini (IV) was to attack Essling. Prince Johann of Liechtenstein's Austrian reserve cavalry was in the center, ready to move out against any French cavalry attacking the heads of the columns. During the 21st the bridges became more and more unsafe, owing to the violence of the current, but the French crossed without intermission all day and during the night.
French
Armée d'Allemagne, under the command of Napoleon I:
Total: 77,000 men (67,000 infantry, 10,000 cavalry), 152 guns
Following the overnight redeployment of Molitor's division between Aspern and Essling, the division is now fully concentrated in Aspern. The recently arrived divisions of Legrand and Boudet have been assigned to Aspern and Essling, respectively. Bessiéres' cavalry occupied the area between the two villages, along a slightly banked east-west road. Lannes, the official commander of II Corps, was given temporary control of Boudet's division and charged with defending Essling, the most vulnerable part of the French position.
Battle
First day
Napoleon had not anticipated a significant engagement on the northern bank. The significant deployment of light cavalry at the head of the crossing schedule suggests that he still anticipated the necessity to locate Charles' army. At 4:00 p.m. on the 21st, Napoleon convened a meeting with his senior military officers to review the latest intelligence and plan the next steps. Despite the expectation that Bessières' advanced cavalry patrols would have discovered the presence of the main Austrian army so close to the bridgehead, they sent back no such information. This suggests that the French reconnoitering cavalry proved ineffective on this occasion. As there were no reports of the enemy, Lannes stated that he believed the army would encounter no more than 8,000 Austrians on the 21st, at the very outside. Only the cautious Masséna made an estimation that the enemy might already be nearby in force, but this was not agreed with by the others.
At approximately 1:00 p.m., the leading elements of the Austrian 1st Corps drove Molitor's outposts back into Aspern. The French were caught off-guard; the attack was hidden by the combination of a low ridge and a convenient dust storm until the last moment. However, Molitor was able to repel the initial attack and gain sufficient time to bring all four of his regiments into the town. Despite repeated Austrian attacks throughout the afternoon, the French defence held firm. However, by 5:00 p.m. the Austrian forces had formed a half-circle around Aspern, and Archduke Charles ordered a general assault. Molitor was now facing significant challenges in maintaining his position, with the enemy launching simultaneous attacks from three directions. In the hours that followed, Aspern changed hands no less than six times. However, Molitor was determined not to concede defeat and continued to hold his position until he could be reinforced by Legrand and Carra St. Cyr. This enabled the vital bridge to be opened to traffic once more.
Meanwhile, in a strategic centerpiece, the 7,000 sabers of Bessières engaged in a prolonged battle against Austrian cavalry and neighboring corps. The garrison at Essling was holding its own on the extreme right. Here, the French forces were only effectively attacked by Rosenberg's 4th Corps from 6:00 p.m. onwards. Due to Lannes' strategic deployment of Boudet's troops positioned within the town, the French successfully repulsed three successive Austrian attacks, maintaining control of their position and preventing significant losses.
Just before 7:00 p.m., the last new personnel arrived on the scene. St. Germain's brigade from Nansouty's division and St. Sulpice's cuirassiers were present for Bessiéres' final assault on the enemy centre, but there were no significant outcomes. With the onset of darkness, the majority of combat ceased, and the two armies settled into a state of relative calm, with the exception of the ongoing engagement at Aspern, where a narrow distance separated the French and Austrian forces. At his new headquarters in Breitensee, Archduke Charles was engaged in planning the next day's operations. Meanwhile, on the nearby island of Lobau, Napoleon was sending urgent messages to Davout in Vienna and mobilising all available troops in the bridgehead.
The bridge remained open for the majority of the night, allowing Lannes' command, comprising St. Hilaire's division and Oudinot's corps of grenadiers (Tharreau and Claparéde's divisions), to safely reach the bridgehead by 4:00 a.m. This contingent was accompanied by additional cavalry and artillery units. The new troops were immediately deployed to secure the central sector of the position, while Bessiéres' cavalry was redeployed to a local reserve position. Boudet's troops were still in control of Essling, with a contingent on their right occupying the open ground. On the left flank, Aspern and its surrounding area were under the control of Legrand and Carra St. Cyr. However, Molitor's depleted regiments, which had been the primary focus of the previous day's fighting, were relocated to a reserve position to the south. In addition, two divisions of the Guard were positioned to defend the bridgehead, and General Demont's division was preparing to cross from Lobau. This brought the French forces to around 50,000 infantry, 12,000 cavalry and 144 guns. They were facing over 100,000 Austrian troops supported by at least 260 artillery pieces.
Second day
Despite the cessation of hostilities in Aspern earlier that evening, sporadic fighting continued throughout the night. At approximately 5:00 a.m., the Austrian 1st and 5th Corps initiated a new full-scale assault on the town and the nearby wooded area known as Gemeinde-Au. This was conducted under cover of darkness and a thick mist. The fortunes of the struggle fluctuated, but a particularly successful counterattack by Massena at approximately 7:00 a.m. resulted in the French recapturing the entirety of Aspern. Meanwhile, Dedovich and Rosenberg leading the fourth and fifth columns, respectively launched a new attack on Essling. Despite making some progress, they were unable to gain the upper hand and were held back by Boudet's forces.