The Black Madonna is said to have miraculously saved the monastery of Jasna Góra (English: Bright Mount) from a Swedish invasion. The Siege of Jasna Góra took place in the winter of 1655 during the Second Northern War, as the Swedish invasion of the Polish–Lithuanian Commonwealth is known. The Swedes were attempting to capture the Jasna Góra monastery in Częstochowa. Seventy monks and 180 local volunteers, mostly from the Szlachta (Polish nobility), held off 4,000 Swedes for 40 days, saved their sacred icon and, according to some accounts, turned the course of the war. This event led King John II Casimir Vasa to give what has become known as the Lwów Oath. He submitted the Polish Commonwealth under the protection of Our Lady and proclaimed her Queen of Poland in the cathedral of Lwów on 1 April 1656. Before this event, several royal nobilities have offered crowns to the image throughout the years, replacing its iron sheet crown riza with one in gold with several jewels. In later years, various gemstones were interchanged and repositioned around the image to preserve the icon's aesthetic with the replacement of stolen crowns.