During the Swedish Wars Chełmno for many months was besieged by the Swedish troops. When the food reserves proved insufficient and the town was threatened with starvation the town councillors decided to surrender the town. Miraculously enough, the townswomen found the way to save the city: they beaked a large loaf of bread which was then fired from the biggest canon on the town towards the Swedish station. Furthermore, the townspeople took an ox and marched with it along the defence wall. The animal mooed so piercingly that made an impression of a huge number of cattle kept in the town. The Swedish soldiers were astounded by apparent proofs of the town’s prosperity in spite of the prolonged siege, and carried out a frenzied attack on Chełmno. However, they were genuinely surprised seeing that their stone canon balls did no harm to the Blessed Virgin Mary, who strolled on the fornications and apparently kept the balls away from city wall. Consequently, the Swedish troops, appalled and terrified by miracle, broke the camp and fled in panic. Several stone balls, (which serve as deterrent), were mounted on the city wall near the monastery to commemorate this supernatural occurrence.