Why the Fortress was built
When in 1525 (after the homage paid to Sigismund the Old, the Polish king, and the secularization of the State of the Teutonic Order), Albert, Duke of Prussia, created the first Lutheran country in the world, he already knew that in order to provide Prussia with the possibility to take the leading role among German countries, it was necessary to conquer Silesia. From the first moments of its existence, Prussia began to make efforts to take the control over Silesia, but in 1532, Albert’s brother, George the Pious, managed to take over the control over the Duchy of Opole only for 10 years. Coming into the inheritance left by Jan the Good was made impossible by the emperor.
A convenient opportunity to take over Silesia appeared on 20 October 1740, when Emperor Charles III died and was succeeded by his daughter, Maria Theresa, via so-called pragmatic sanction. The King of Prussia, Frederic the Great, did not hesitate to break the sanction signed by his father, Frederic I, and immediately began preparing for war. On 16 December 1740, the Prussian army entered Silesia. The fate of the province was sealed by the defeat of the Austrian army in the Battle of Mollwitz on 10 April 1741. During the following years, two more wars were fought over Silesia, but the Habsburgs did not manage to reclaim it.
Soon after experiencing the Thirty Years’ War (1618-48), the Austrian authorities came to the conclusion that the fortifications of the Silesian fortresses had to be upgraded. Koźle appeared among the towns selected to be turned into modern fortresses (Wrocław, Brzeg, Nysa, Kłodzko, Głogów). At the beginning of the 18th century, the construction of bastion entrenchments on the plane of an eight-pointed star was planned. There is no proof that these plans moved beyond the design stage. After taking over Silesia, the King of Prussia, Frederic the Great, began to vigorously upgrade the Silesian fortresses and built a fortress in Koźle. General Gerhard von Walraw became the manager of the project. This time, it was planned that the bastions would be built on the plane of a five-pointed star based on the Odra river. For this purpose, a hospital and a small church at ul. Raciborska, as well as the monastery of Friar Minors and the monastic church near the Odra river, a cemetery, gardens, and several houses near the Racibórz Gate, were demolished. The fortifications were not ready yet when Maria Theresa attempted to reclaim Silesia in 1744. Consequently, in 1745, the imperial army took over Koźle and immediately began to finish the Prussian plans. They were carried out thoroughly enough for Prussians to need a three-month siege in order to reclaim Koźle. Of course, after taking over Koźle, they resumed the development of the fortification.