Editing Battle of Wagram (section)

=== Opening campaign ===
By March 1809, war between Austria and France was imminent and the [[Habsburg dynasty|Habsburg]] army, 200,000 men strong, massed in the northwestern province of [[Kingdom of Bohemia|Bohemia]], near the frontier with the [[Confederation of the Rhine]], the French-dominated confederacy of German states. Austria hoped that Prussia would join the war and, by massing its main army in Bohemia, it signalled its intent to join up with the Prussians. However, by early April 1809, it became obvious that Prussia was not ready to commit, and the Austrians were forced to move their main army southwards, in a bid to launch their westward offensive along the [[Danube]]. Strategically, the decision was sound, since an offensive along the river valley allowed better protection for the Austrian capital. Nevertheless, the time-consuming manoeuvres to Bohemia and back cost the Austrians an entire month.{{sfn|Rothenberg|1995|pp=62–63}}<ref>Fierro, Palluel-Guillard, Tulard 131–137 and 586.</ref>
[[File:Eckmuhl April 15.jpg|thumb|250px|Opening moves: strategic situation on 15 April]]
On 9 April 1809, without any declaration of war, the main Austrian army crossed the [[Inn (river)|Inn River]] into [[Kingdom of Bavaria|Bavaria]], one of France's main allies, while secondary Austrian armies launched offensives of their own. Meanwhile, Napoleon was in Paris, conscious that the war was imminent but unaware that the Austrians were prepared for immediate offensive. Command of the French and allied army, styled ''[[Army of Germany (1809)|Armée d'Allemagne]]'', was in the hands of ''[[Marshal of the Empire|Maréchal]]'' [[Louis-Alexandre Berthier|Berthier]], a formidable officer when working as Napoleon's [[chief of staff]], but completely out of his depth as a commander by proxy.{{sfn|Rothenberg|1995|pp=65–82}}Furthermore, in order to remain in close contact with Paris by military telegraph and to avoid provoking the Austrians, Berthier was initially ordered to set up his headquarters near Strasbourg, hundreds of kilometres away from the front line, before moving to Germany as war broke out.{{sfn|Chandler|1998|p=670}} As a result, Berthier's response to Charles's invasion was timid and, after misinterpreting Napoleon's orders, he left two entire army corps in isolated positions. Consequently, during the first week of the campaign, Charles was able to advance virtually unmolested and take advantage of the poor French deployment. All changed from 17 April, when Napoleon arrived in person and began concentrating his available troops to meet the Austrian onslaught. Before Napoleon could concentrate his corps, Charles attacked [[Louis-Nicolas Davout|Davout]]'s isolated corps at [[Battle of Teugen-Hausen|Teugen-Hausen]] but the dogged French marshal repulsed the attackers. The tide of the campaign had turned but Napoleon misjudged the strategic situation, thinking that the force that had fought Davout was only a flank guard and that the main force lay before him; in reality it was the opposite. As the French took the offensive several actions ensued : [[Battle of Landshut (1809)|Landshut]], [[Battle of Abensberg|Abensberg]], [[Battle of Eckmühl|Eckmühl]] and [[Battle of Ratisbon|Ratisbon]], with the Austrians coming off worse each time and having their left wing cut off from the bulk of the army. In the end, however, Charles succeeded in avoiding a decisive defeat, preserving a combat-ready army which he directed north of the Danube, where he awaited Napoleon's next move.{{sfn|Rothenberg|1995|pp=65–82}}
[[File:Eckmuhl April 21.jpg|thumb|250px|Battles of Eckmühl and Ratisbon]]
Charles's retreat left Napoleon with two options: pursue the defeated Austrian army north of the Danube or occupy Vienna, which was now covered by a secondary enemy force and could not hope to hold out. Uncharacteristically, Napoleon, who had stated on a number of occasions that the purpose of any campaign is to destroy the main army of the enemy, opted for the latter course of action and entered the enemy capital on 12 May, only to find the city's strategic bridges over the Danube blown up. With the emperor poised for an immediate continuation of the offensive north of the river, this was a considerable setback. Meanwhile, Charles brought the bulk of his remaining force on the northern bank of the river, close to Vienna, which lured Napoleon into attacking them right away. Napoleon's rushed crossing of the river was made on fragile, hastily built pontoon bridges, over an increasingly swollen river. The French crossing resulted in the [[Battle of Aspern-Essling]], beginning on 21 May; the more numerous Austrian army faced only a fraction of the {{lang|fr|Grande Armée}}, as Napoleon was unable to bring through the bulk of his forces in time. Still, Charles's attempt to drive the outnumbered enemy back resulted in total failure, as the French led a skillful combined-arms defense, with their cavalry playing a vital role in keeping the Austrians at bay. Fighting resumed early on 22 May, when Napoleon began receiving some reinforcements and decided to attack. The French offensive was quite successful but Napoleon soon received alarming news that the main bridge had broken and consequently, no further reinforcements and ammunition could be brought from the southern bank, making a protracted battle impossible. This prompted the emperor to immediately stop his attack and order a phased retreat onto the large Danube island of Lobau. Given that the Austrians, with their superior numbers and overwhelming artillery firepower, were now intent upon seizing the opportunity to launch a counterattack of their own, retreat was most difficult. It took all the experience of the French commanders and the determination and self-sacrifice of the troops, including the [[Imperial Guard (Napoleon I)|Guard]], to fend off the ferocious Austrian onslaught but, by nightfall, the remains of the French forces were safely across the arm of the Danube, on the island of Lobau. Napoleon had suffered the first significant defeat of his career.{{sfn|Rothenberg|1995|pp=85–129}}{{sfn|Castle |1990|pp=29–55}}<ref>Fierro, Palluel-Guillard, Tulard 138–139 and 586.</ref>