The battle of Alessandria or Cassina-Grossa (20 June 1799) was a rare French victory in Italy during the campaign of 1799, but one that came too late to prevent the Austro-Russian army of Marshal Suvarov from defeating a second French army at the battle of the Trebbia (17-19 June 1799)
At the start of the War of the Second Coalition the Austrians and Russians won a series of victories that threatened to push the French completely out of Italy. The first of these victories, at Verona and Magnano, saw the Allies defeat French offensives, but at Cassano (27 April 1799) it had been Marshal Suvarov who had taken the initiative. In the aftermath of this victory the Allies had taken Milan, and the French, now under General Moreau, had been forced to retreat to Genoa.
The French had a second army in Italy, the Army of Naples under General Macdonald. After the defeats in the north Macdonald was ordered to move north to combine with Moreau in an attempt to overcome the Allies' numerical advantage.
Suvarov realised the danger he was in, and moved against General Macdonald. The two armies clashed on the southern bank of the River Po, just to the west of Piacenza (battle of the Trebbia, 17-18 June 1799). After three days of fighting Macdonald was forced to admit defeat and retreat east, without meeting up with Moreau or any of his forces.
If Moreau had moved as quickly as Macdonald then the two French armies would almost certainly have been united, but his first move didn't come until 16 June when he dispatched General Lapoype north-east towards Bobbio to join up with Macdonald. This placed Lapoype just to the south of the fighting on the Trebbia, but Lapoype spent three days outside Bobbio. Only after the battle was over did he advance north, in an attempt to protect Piacenza. Suvarov learnt of this move, and sent a column to capture Bobbio. Lapoype realised he was cut off, and attempted to fight his way back through Bobbio. After this failed he moved east into the Taro valley, where he joined up with General Victor, with part of Macdonald's left wing. This combined force was able to hold the mountain passes, and helped Macdonald reach Genoa along the coast.
Moreau's main advance began on 17 June. The French left Genoa in two columns. After crossing the mountains the left, 4,500 strong, advanced north-west up the main road toward Novi, while the right, 9,500 strong, crossed the river Scrivia, and advanced north along the foot of the mountains towards Tortona. Bellegarde had orders to hold the French back for as long as possible, and so retreated slowly back towards Alessandria. On 18 June he lifted the siege of Tortona, and withdrew west to Spinetta, between there and Alessandria. Bellegarde had 8,000 men with him, while Vukassovich had a similar force behind the Bormida (south-west of Alessandria). This gave the Austrians around 16,000 men and the French 14,000.
On 19 June Moreau, with Grenier's division, advanced towards Tortona, which was being besieged by an Allied force under the Austrian general Heinrich Bellegarde. On the same day Moreau had Quesnel's and Partouneaux's brigades camped on the right bank of the Scrivia, and Grouchy spread out as far as Torre Garofoli, on the road west of Tortona.
Moreau decided to attack Bellegarde's camp at Spinetta. Garreau's, Serras's and Colli's brigades were to cross the Scrivia and advance west towards Cascina Grossa (Cassina-Grossa in early French sources), a small village just to the east of Spinetta.
The advance began early on 20 June. Garreau, on the French left, pushed the Austrians out of Pozzolo, but then turned too far to the right, and instead of moving north-west towards Cascina Grossa moved north towards Quattro Cascine. This put him on the same track as Serras, in the French centre, and both brigades ended up at San Giuliano, two miles east of Cascina Grossa.
They were soon joined by Grouchy, with Colli's brigade. Moreau decided to attack the Austrian position at Cascina Grossa. The battle for the village was hotly contested. The French captured the village at least twice, and were forced out by reinforcements from Spinetta. Bellegarde decided to try and envelop Garreau, on the French left, and greatly extended his own right wing. This led to the decisive moment of the battle, when Moreau, with Grenier's division, attacked the centre of Bellegarde's line, cutting off the Austrian right, most of which was either captured or killed.
This disaster forced Bellegarde to retreat west behind the line of the Bormida. The Austrians had lost 3,000 men, 1,500 of them prisoners. Bellegarde retreated south-west to Castelnuovo-Bormida, while the French occupied the plains around Tortona.
This was a significant French victory, and if it had come a week earlier might have been of great importance, for it would have allowed Moreau to join up with Macdonald having already defeated part of the Austro-Russian army. Instead it came a day after Macdonald's defeat on the Trebbia. When Moreau learnt of this defeat, he realised that he would have to retreat back to Genoa.
Moreau's victory did help Macdonald escape from Suvarov's pursuit. Macdonald had fought rearguard actions at San-Giorgio (20 June 1799) and Sassuolo (23 June 1799) and the Allies were pressing him hard. When Suvarov heard that Bellegarde was in some danger he called off the pursuit, gathered his scattered army and moved west. On the night of 25-26 June, with Suvarov approaching from the east, Moreau slipped away from Tortona and retreated into the mountains at Gavi and Novi, before retreating back to Genoa. Macdonald was also able to reach Genoa, crossing the Apennines further east and advancing west along the coast. Moreau was replaced as commander of the combined army by General Barthélemy Joubert, who led it to yet another defeat, at Novi on 15 August 1799, dying in the battle.