Mantua was one of the most formidable fortresses in Italy. The city was strategically important for projecting Austrian power in Italy because it was a well-placed supply center and staging point for soldiers. The critical line of communications from Austria to Italy began in
Innsbruck and traced to Mantua via the
Brenner Pass and the
Adige River valley. However, the fortress required a garrison of 14,000 troops to properly defend it. The city was surrounded on three sides by a lake formed by the
Mincio River and on the last side by marshes. On 14 May, Canto d'Irles reported that his garrison numbered only 2,154 soldiers and that there were severe shortages of food, money, and artillerymen. Nevertheless, there were ample stocks of ammunition, firearms, 76 mortars, and 179 heavy siege guns. In mid-May,
Feldzeugmeister Johann Peter Beaulieu reinforced Mantua's garrison with substantial numbers of soldiers. Canto d'Irles assigned these troops to guard an outer defense line, to repair the fortifications, and to bring in food from the surrounding area.
Napoleon Bonaparte's French army defeated Beaulieu's Austrian army in the
Battle of Borghetto on 30 May 1796. On 2 June, the first French soldiers appeared outside the city. By this time, there was enough bread and flour to last 71 days, oats for 124 days, hay for 22 days, and wood for 54 days. The city was notorious for epidemics of
malaria which people mistakenly attributed to bad air. By the time that the French surrounded Mantua on 3 June 1796, Canto d'Irles commanded a garrison of 13,753 soldiers. These were distributed as follows: Generalmajor
Gerhard Rosselmini held the
citadel with 3,666 men, Generalmajor
Josef Philipp Vukassovich defended the Pradella hornwork with 2,449 soldiers, Generalmajor
Mathias Rukavina von Boynograd guarded the Migliaretto with 2,443 troops, Oberst Salisch occupied the Palazzo Tè crownwork with 1,489 men, and Oberst Strurioni held the San Giorgio suburb with 2,298 men. Other defenders included 96 military engineers, 701 gunners, and 434 cavalrymen. The French did not lay
siege to Mantua early in June because there was no siege artillery available and because the land around the city was flooded. So instead, Bonaparte's forces raided the
Papal States and the
Duchy of Modena and Reggio, extorting large sums of money and seizing siege artillery. The Mantua garrison foiled a serious French attack on 16 July 1796, though Austrian casualties were 70 killed, 330 wounded, and 64 captured. Having assembled sufficient siege guns, the French opened a bombardment of Mantua's defenses on 18 July and it continued for many days. A letter from the new Austrian army commander
Field Marshall Dagobert Sigmund von Wurmser was smuggled into the city telling Canto d'Irles that he would be relieved by 2 August. Wurmser relieved Mantua on 1 August 1796. In order to fight Wurmser's army, the French withdrew from the city, abandoning all their artillery. French losses were about 1,200 men killed and wounded, and 898 men and 174 artillery pieces captured. The Austrian garrison lost 120 killed, 395 wounded, and 74 captured in combat. Also, 372 men died of disease and 13 men deserted. From 1–10 August, the Austrians destroyed all the French siege works and removed all the captured guns into the city. However, Wurmser was defeated by Bonaparte at the
Battle of Castiglione on 5 August and was compelled to withdraw from the vicinity of Mantua. At the time of its relief, 3,275 men from Mantua's garrison suffered from illness. On 2 August, Wurmser asked Canto d'Irles for reinforcements, but only 2,000 men could be spared from the garrison. On 6 August, an inspection found that the garrison counted only 10,788 men of whom only 7,455 were fit for combat. Canto d'Irles asked for a garrison of 20,000 men if the Austrian army retreated. He was authorized to borrow money from the city's inhabitants to pay the soldiers and to buy supplies. An
engineer, Feldmarschall-Leutnant
Franz von Lauer arrived to help repair the fortress. The garrison was reinforced by 7 infantry battalions and 1 cavalry squadron under Generalmajors Ferdinand Minkwitz and Leberecht Spiegel. This brought the garrison to 16,423 men, but only 12,224 were fit for service. On 10 August 1796, Canto d'Irles was awarded the Commander's Cross of the Military Order of Maria Theresa. On 8 September 1796, Bonaparte's French army routed Wurmser's army at the
Battle of Bassano. Wurmser evaded all French attempts to keep him from reaching Mantua and appeared before the city with 10,367 infantry and 2,856 cavalry on 14 September. The next day, Bonaparte defeated Wurmser's forces, inflicting 2,452 casualties and forcing the survivors within Mantua. The garrison swelled to 29,676 men, but within six weeks 4,000 died from disease or battle injuries. Canto d'Irles was still technically the fortress commander, but he fell sick and was now outranked by Wurmser. Mantua finally surrendered on 2 February 1797. Wurmser and his generals were allowed to go free with 500 infantry, 200 cavalry, and 6 guns, while 16,324 soldiers became prisoners of war until they could be exchanged. These were only survivors of 30,475 men of the garrison. Gravely ill, Canto d'Irles began to travel to Vienna, but he died on the way at
Varaždin in
Croatia on 11 April 1797. ==See also==