The battle of the Trebbia (17-19 June 1799) was a major Allied victory over the French Army of Rome that further weakened an already poor French position in Italy at the start of the War of the Second Coalition. When that war began the French and Austrians were facing each other across the Adige River, but the French suffered defeats at Verona (26 March 1799) and Magnano, (5 April 1799) and were forced back towards Milan. The Austrians were then joined by a Russian army under Marshal Suvorov. The Allied army forced their way over the Adda River (battle of Cassano, 27 April 1799), and captured Milan. General Moreau was forced to retreat to the coast around Genoa, while the French Army of Rome, under General Macdonald, was ordered to move into northern Italy.
Macdonald advanced from Rome to Florence, and then in mid June crossed the Apennines and emerged on the northern Italian plains close to Modena. From there he advanced rather too slowly up the Po towards Piacenza. General Moreau planned to advance north from Genoa to Alessandria, then turn east to join up with Macdonald. General Victor was sent north east from Genoa, and joined Macdonald before the battle, giving Macdonald just over 30,000 men.
When Suvorov learnt that Macdonald was approaching, he decided that he could not let the two French armies unite. General Karl Ott, with around 12,000 men, was posted on the Trebbia, but it was clear that he would soon be overwhelmed by the advancing French, and so on 15 June Suvorov, at the head of 24,000 men, set off towards Piacenza. His men covered thirty miles in twenty four hours, proving that the French army was not the only one capable of such rapid movement.
The battle took place west of Piacenza on the plains between the Po and the Apennine Mountains. The Trebbia and Tidone rivers run north from the mountains to join the Po, the Trebbia just to the west of Piacenza, the Tidone a little further to the west.
The battle began as a clash between General Karl Ott's corps and the French advance guard (Victor, Dombrowksy and Rusca). Ott was pushed back from the Tidone River to Sarmato and Castel San Giovanni. At this point the French were spread out between the Tidone and the Nura rivers, and were thus vulnerable to a counterattack.
Ott sent urgent messages west asking for help from Suvorov, who by now was approaching the battlefield. Suvorov lined up with Bagration on his left, facing Victor close to the Po, Ott in the centre facing Dombrowsky and Melas on the right facing Rusca.
At first the French held their own. Victor pushed Bagration back along the Po, but Dombrowsky was less successful. The Russian infantry held him in place, and then the cavalry forced the Poles to retreat. The cavalry then hit Victor's left flank and forced him to retreat back across the Tidone and towards the Trebbia. Macdonald then decided to form a new line on the Trebbia and wait for his remaining divisions to arrive from the Nura.
On 18 June Suvorov took the initiative. Rosenberg, with Bagration's and Schweikofsky's divisions, was to cross the Trebbia close to Rivalta, close to the Apennine range at the southern end of the line. That morning Macdonald was rearranging his lines. Dombrowsky, Rusca and Victor were moved to the French left, where they would face the Allied attack. Olivier's and Montrichard's divisions were to make up the centre of the line and Watrin the French right.
Suvorov's planned attack was pre-empted by Victor. Early in the morning the Russian advance guard pushed the French out of their advanced posts at Casaliggio and Gragnano in the centre of the line and Victor responded by crossing the Trebbia. He was pushed back by Rosenberg, but the Allies were unable to make any more progress. Most of the fighting on 18 June took place at the southern end of the line, and elsewhere was limited to a cannonade.
Overnight an impromptu battle broke out when a French unit moving into place in preparation for Macdonald's planned attack on 19 June was mistaken for a general assault. After some costly fighting the generals on both sides managed to get their troops under control and the fighting died down.
On 19 June Macdonald planned to attack at both ends of the line. Dombrowsky was to attack at Rivalta on the French left, while Watrin was to attack along the Po at the right. Both armies were now of similar size – the Allies had 35,000 men and the French 33,500, but Suvorov was still receiving reinforcements while Macdonald was now at his maximum strength.
On the morning of 19 June Dombrowsky crossed the Trebbia at Rivalta. Suvorov responded by moving Bagration's division to support the Allied right, but this left the flank of Schweikofsky's division of Rosenberg's corps exposed. Victor and Rusca advances across the Trebbia and enveloped Schweikofsky, temporarily trapping Suvorov. Having restored the situation around Rivalta Bagration returned north and restored the line.
In the centre of the line Montrichard crossed the river opposite Grignano, Oliver crossed further north opposite San Nicolo and Watrin advanced along the Po. Montrichard and Olivier threatened to overwhelm General Ivan Förster's division, but their advance exposed them to a counterattack by the Allied reserve, under General Melas, which was moving south to go to Suvorov's aid. Supported by General Johannes Fürst zu Lichtenstein's cavalry the reserve forced Montrichard to pull back across the Trebbia. Lichtenstein's cavalry then attacked Olivier in the flank and forced him to pull back from San Nicolo.
At the north of the line Watrin had reached Calendasco, from where he could have outflanked the Allied left, but with Montrichard and Olivier retreating Watrin had no choice but to pull back to the Trebbia.
This ended the battle. Macdonald was aware that he could expect to receive no more reinforcements, while Suvorov was still getting stronger. The French suffered 9,000 casualties during the fighting, while the Allies lost around 5,500 men. The Allies also captured 7,000 wounded French soldiers in Piacenza.
On the night of 19-20 June the French pulled back to the Nura. From there Macdonald escaped across the Apennines to the coast then advanced up the coast to Genoa, where with the surviving half of his army he managed to join up with Moreau.