| Conflict: | Siege of Brno |
| Partof: | the Thirty Years' War |
| Date: | 3 May – 23 August 1645 |
| Place: | Brno, Margraviate of Moravia, Habsburg monarchy (now the Czech Republic) |
| Coordinates: | 49.1925°N 16.6083°W |
| Result: | Imperial victory |
| Combatant1: | Swedish Empire |
| Combatant2: | Holy Roman Empire |
| Commander1: | Lennart Torstensson Arvid Wittenberg |
| Commander2: | Jean-Louis Raduit de Souches Georg Jacob Ogilvy Martin Středa |
| Strength1: | c. 28,000 soldiers in total (including reinforcements led by Sigismund II Rákóczi) |
| Strength2: | c. 426 soldiers, plus c. 1000 armed men from local militia |
| Casualties1: | c. 8,000 dead and wounded |
| Casualties2: | c. 250 dead |
The Siege of Brno, which occurred from 3 May 3 to 23 August 1645, was the second Swedish siege of the city of Brno in the last years of the Thirty Years' War.[1] The Brno garrison, consisting of 500 soldiers and about 1,000 Brno residents, successfully defended the city against about 28,000 soldiers of General Lennart Torstensson. The success of the defenders was the starting point of a brilliant career for their commander, Jean-Louis Raduit de Souches,[2] in the service of the Habsburgs; siege kept the Swedish army occupied for several months. This Austrian victory ultimately contributed to Brno becoming the metropolis of Moravia, at the expense of the conquered Olomouc.
In 1636, Emperor Ferdinand II of Habsburg made Brno the metropolis of Moravia, as he had established his governorship here, the so-called "Royal Tribunal". In 1642, Brno became the seat of all royal and state offices, as the politically more important Olomouc had been occupied by invading Swedes since 1642.[3] When the danger of an expected Swedish attack became clear, some state dignitaries fled to Vienna. Brno was then unsuccessfully sieged by the Swedish army in 1643.
On 31 January 1645, the Swedes invaded the lands of the Bohemian Crown via the Ore Mountains and on March 6, in the Battle of Jankau,[4] they defeated the imperial army of Ferdinand III. For Swedish general Torstensson, who just finished the campaign called Torstenson War, and his army this victory opened the way for the march on Vienna. The situation forced him to stop in front of the Austrian metropolis, however, as his army was now clearly exhausted and lacked the supplies that were essential for besieging a large city. The Danube river also represented a difficult hurdle to overcome. Therefore Torstensson moved to Moravia, Olomouc Fort specifically, which had been conquered in 1642 and gave the Swedes access to the delivery routes into Moravia, and established there the operational base of his forces. Only one important fortress now stood in the way of the planned advance to Vienna: the city of Brno.
On 14 March 1645, the emperor appointed the 37-year-old colonel of French descent, Jean-Louis Raduit de Souches, as the commander of the city. The Frenchman initially enjoyed little trust among the citizens of Brno, not just because he was a Protestant Huguenot. He immediately began to prepare the city and its modest forces for a long siege.
He and the then city captain decided that the city's defensive structures should be renovated and fortified or rebuilt. All buildings that were 600 paces or closer to the city walls were demolished, old ditches were deepened, and new ones dug in their places. To ensure that the city's population could be fed, a mill driven by a group of oxen was built, and all the city's wells were cleaned. A hidden road (strada coperta) then connected the city with the Špilberk fortress. Commander de Souches soon gained respect through his determination and attitude to securing the city's defenses. He countered a severe shortage of weapons with intensive production, in which the city's population participated. The number of defenders was small, 1,475 men were armed, of whom only 426 were soldiers, and the moderate force was supplemented by practically all of the city's able-bodied men, since Brno itself had perhaps 5,000 inhabitants, including women and children. Nevertheless, everyone was determined to withstand the besieging Swedes' 18-fold superiority. At the beginning of May 1645, everything necessary was brought in just in time. Equipment consisted of muskets, fortress cannons, but also makeshift scythes and other improvised peasant weapons.
The siege of Brno started 3 May 1645 when Torstensson and his army reached the city.[5] After the failed negotiations Swedes started the attack and artillery bombardment of the city and the Špilberk fortress, but without a bigger successes. Brno defenders were able to push back Swedish attacks and also made a several quick attacks outside the city walls. Morale of the defenders was also boosted thanks to a joinment of a Jesuit priest Martin Středa,[6] who called Brno citizens in arms. Although, in July, Swedes were able to dig the tunnels under the fortification walls and create a light damage to the structure by firing up gunpowder mines. At 26th of July were Swedes supported by the forces of Sigismund II Rákóczi[7] with the forces of about 10 000 men: their mostly light cavalry men weren't able to contribute to the military successes, but two heavy cannons joined the Swedish fire power.
After Torstensson, in the beginning of August, realized that Rákóczi family was negotiating with the emperor about peace, he ordered to prepare the last attempt to conquer the city. That occurred on August 15, 1645. All through the long battle, Swedes weren't able to penetrate Brno defence. Eight days later, on August 23, Torstensson ordered his exhausted forces to withdraw.[8] [9] Swedes lost about 8,000 men dead and wounded.
The exhausting and failed siege of Brno forced the Swedes resume the military operations in the area around Vienna. The successful operations of the imperial forces in Bohemia and Silesia prevented Torstensson's successor, Lieutenant General Arvid Wittenberg, from making further advances into what is now the Austrian state of Lower Austria in the following year. The Swedish garrisons on the Danube and in the other parts of the country were therefore left to their own devices, which pretty much contributed to their recapturing, especially of the two important Swedish fortresses of Krems and Korneuburg.