The battle of Palestro (30-31 May 1859) was a Piedmontese victory over the Austrians that helped cover the movement of their French allies from their original position on the Austrian left to a new position on the weaker Austrian right, and that prepared the way for the first major Allied victory of the Second War of Italian Independence, at Magenta.
At the start of the war the Piedmontese had been outnumbered by the Austrians, and their main task had been to hold onto the rail head at Alessandria until the bulk of the French army could arrive at Genoa. By 12 May the danger of a quick Austrian victory had passed. The French had arrived in numbers and Napoleon III arrived to take personal command. The Austrians, under Feldzeugmeister Franz Count Gyulai, realised that the main danger came along the Po, and abandoned any plans to threaten Turin. By mid-May the Austrians were arranged in a west-east line that ran from Vercelli in the west, through Mortara and on to Pavia, with another corps further east at Piacenza. Austrian attention was further focused in the south after the battle of Montebello (20 May 1859), a French victory won on the edge of the Apennines south of the Po.
In the aftermath of this battle Gyulai moved his army once again. VII Korps was posted on the Sesia, watching the approaches to Mortara from the west. VIII Corps was moved from Pavia to the confluence of the Sesia and the Po. II and III Korps were south of Mortara. V Korps was on the Po at Pavia and IX Korps was at Piacenza, at the Austrian left. The Austrian commanders expected the Allies to try and move east on the southern side of the Po to get behind their lines.
The Allies spent the next week after Montebello decided what to do next, and eventually decided to take a calculated gamble and use the Piedmontese railway network to move from the Austrian left to the Austrian right. If the Allies could cross the upper reaches of the Sesia River and reach Novara they would be able to threat Milan, and strike the Austrians where they were weakest.
A number of deceptive measures were put in place to prevent the Austrians from realising what was going on. In the south two French corps remained in place and threatened to cross the Po. In the centre of the line the burden fell on the Piedmontese army. This would form the right wing of the Allied army once the move would complete, but for the moment its task was to shield the French move by going onto the offensive. It would cross the Sesia at Vercelli and attack the Austrian right around Mortara. The aim was to attract the attention of the Austrian right wing and prevent them from interfering with the much larger movement going on behind the front. The attack would also create a bridgehead over the Sesia.
Victor Emmanuel was able to commit four infantry divisions to the attack. The Sesia flows past the eastern side of Vercelli, then turns east, before turning south against close to Palestro. The Piedmontese divisions were to advance east and occupy a line running north from Palestro. Fanti's 2nd Division was to be at the northern end of the line, at Confienza. Cialdini's 4th Division would be at Palestro. Durando's 3rd Division was heading for Vinzaglio, in the centre of the line. Finally Castelborgo's 1st Division formed the reserve and was posted behind Fanti on the Piedmontese left.
The nearest Austrian forces were from Zobel's VII Korps. Zobel had outposts at Confienza and Palestro, and stronger forces at Robbio, to the south-east. One of his divisions was too far south to intervene at Palestro, but he could call on Jellacic's Division from II Korps, which was posted further to the east.
On 30 May Vinzaglio and Palestro were defended by the equivalent of a single battalion. Their positions were attacked by Cialdini's and Durando's Divisions, so they were massively outnumbered. Although reinforcements did reach both positions during the first day's fighting, the Austrians were unable to hold them. Palestro fell by 4.30, Vinzaglio two hours later.
Overnight both sides attempted to rush reinforcements to the area. The French wanted to move Canrobert's III Corps into place, but heavy rain meant that the river rose and only 2,600 men from the 3e Zouaves managed to get across. Even so the Piedmontese had three full infantry divisions in their front line and one in reserve.
Zobel managed to assemble four brigades at Robbio, two of his own and two from II Korps. This gave him just under 14,000 men, about half the size of the Piedmontese front line force. One brigade was kept in reserve. A second was sent to make a flanking attack on Confienza. Finally two were sent to attack Palestro.
The flanking attack was a total failure. Weigl's brigade was outnumbered four-to-one by Fanti's division, and was unable to make any progress.
The attack on Palestro was more successful, at least at first. Dondorf's brigade attacked from the east while Szabo's brigade came in from the south, advancing up the Sesia. Dondorf was stopped east of Palestro, but Szabo managed to get around Cialdini's right flank. The Austrians managed to open fire on Canrobert's pontoon bridge, and for a moment posed a serious threat to the Allied position.
This brief Austrian success was ended by the 3e Zouaves. They had taken up a position close to the Sesia, behind a side branch of the river called the Sesietta (the same name is sometimes given to the island formed between the main river and the branch). The Austrians had advanced right past the Zouaves, who were hidden behind some trees. The Zouaves formed up and charged into the left-rear of the Austrian troops. Jäger Battalion 7, the lead Austrian unit, was forced back while all of Szabo's guns were captured. The rest of his brigade fled, suffering heavy casualties when the Allies managed to seize a key bridge.
After this setback Zobel called off the attack and withdrew to Robbio. The Austrians had suffered over 2,000 loses during the day, nearly three times as many as the Allies, who had lost 600. The Zouaves had suffered most heavily, loses 46 dead, 229 wounded and 20 missing. Remarkably Victor Emmanuele had taken part in their charge and on the following day the regiment made him an honorary corporal.
It took the Austrians several days to realise that this battle was part of a much larger French movement. When it finally became clear what was happening Gyulai decided to abandon his invasion of Piedmont, and on 2 June the Austrians began to retreat back to the Ticino, re-crossing into Lombardy to defend Milan. This would be a short-lived effort, for on 4 June they would suffer a major defeat (battle of Magenta, 4 June 1859), and would be forced to abandon Milan and Lombardy and retreat back towards Venetia.