The battle of Sacile (16 April 1809) was the first major battle during the War of the Fifth Coalition, and was an Austrian victory that might have caused the French serious problems in Italy if events on the Danube had not forced the Austrians to pull their army back.
At the start of the War of the Fifth Coalition the Kingdom of Italy was a French satellite, ruled for Napoleon by Eugène de Beauharnais. Prince Eugène commanded 68,000 men in the Army of Italy, and by the start of the war most of these men were in the north-east of Italy. The 1st division was furthest east, at Udine, along with a division of light cavalry. The 2nd division was just to the west, on the Tagliamento River, and the 3rd was around Sacile. Next in line was the 5th Division, spread out from Bassano and Cittadalla to Treviso. An advance guard of the 4th Division had just reached Verona, and the rest was on its way. The 6th (or 1st Italian) Division was just to the south of the 5th, around Padua. The 7th (or 2nd Italian) Division was furthest away, in camps at Montichiari to the west of Verona. Two divisions of Dragoons was south of Verona, and the grand park of the artillery was at Verona.
Napoleon was expecting the Austrians to send around 100,000 men across the Alps into Italy, and was caught out when they only sent 50,000 regulars, in two corps, under the command of Archduke John. This meant that the Austrians were much stronger on the Danube than Napoleon had expected, and nearly led to disaster on that front.
On 9 April envoys from the Archduke brought the declaration of War to the French lines. Eugène, who was at Udine, moved west towards Venice, expecting the Austrians to advance at their normal leisurely pace and give him time to concentrate his army. He would be caught out. The first contact was made on 10 April, in the Fella Valley, and the first significant fighting came on 11 April, at Ospedaletto, on the Tagliamento River. Broussier's 1st Division was forced back along the river, and ended the day guarding the bridge at Dignano.
On the night of 11-12 April Eugène ordered his forces to concentrate on the west bank of the Tagliamento. It soon became clear that the Austrians would reach that river in force long before the French would be ready to resist them, and so Eugène ordered his forces to concentrate further west, on the Livenza River. His own headquarters were at Sacile. By 14 April five of his infantry divisions and the light cavalry were close to Sacile. The 1st (General Seras) was at Brugnera, to the south. The 3rd (Grenier) was at Fontanafredda, to the north-east. The 5th (Barbou) was at Fretta, to the west of Sacile. The 6th (Severoni) was at Bibano, to the south-west. The light cavalry was at Pordenone, to the east of Fontanafredda. Finally Broussier and the 1st Division were at a place named as Gardaso in early French sources, probably somewhere to the north-east of Sacile.
While Eugène was concentrating around Sacile the Archduke continued to advance westwards. On 15 April the Austrian advance guard forced the French light cavalry out of Pordenone. Eugène appears to have believed that he was only facing part of the Austrian army, and decided to launch a counterattack on the following day, despite not having his entire army to hand. He also expected to receive reinforcements during the day.
Eugène placed Sera and Severoli divisions on his right, Grenier and Barbou in his centre and Broussier on the left. The light cavalry under Sahuc formed the reserve. The Austrian line ran north from the town of Porcia, due east of Sacile. Eugène decided to start with an attack on the far left of the Austrian line, at the village of Palse, south of Porcia. This attack, which was carried out by Sera and Severoli, was repulsed by an Austrian column from Porcia. The French then attacked again, this time with help from Barbou, and the Austrian troops at Palse were forced to retreat. They were unable to hold on to Porcia, which fell to the French at about noon.
After the fall of Porcia Eugène ordered his left and centre to join the fight. Broussier was ordered to move from Frontanafredda to occupy some hills to the left and rear of Porcia, while Barbou acted as his link with the rest of the army. The entire French army was now involved in the fight, while the Archduke was still gaining in strength. In mid-afternoon the Archduke launched a two-pronged attack, with one prong attacking Porcia while the other attempted to outflank the French. Eugène realised that he could no longer hold onto Porcia or his current line, and ordered his infantry to retreat back to their original camps around Sacile. The French light cavalry successfully covered this retreat, but it soon became clear that the position around Sacile was no longer tenable, and Eugène ordered a retreat to the Adige, reaching his new lines on 22 April. On the Adige he was joined by Lamarque's infantry division and one division of dragoons.
The French and Italians lost between 6,000 and 8,000 men at Sacile, about twice as many casualties as the Austrians. Eugène's position was significantly weakened by the defeat, and instead of the French pinning down 100,000 Austrians in Italy, it was the Austrians who were pinning troops that Napoleon really needed on the Danube. It would be news from that front that would force the Austrians to abandon their strong position in Italy. In mid-April Napoleon arrived on the Danube to take command in person, and defeated the Austrians at Abensberg (20 April), Landshut (21 April), Eggmuhl (22 April) and Ratisbon (23 April). In the aftermath of these defeats the Austrian high command ordered the Archduke John to pull back from the Adige, but to stay as near as possible to his hereditary lands in Italy.