The Königsberg fortifications were erected due to the vulnerability during which war of 1563-1721?
Königsberg fortifications: The fortifications of the former East Prussian capital Königsberg (now Kaliningrad) consist of numerous defensive walls, forts, bastions and other structures. Königsberg fortifications:  The 15 metre-thick First Belt was erected due to Königsberg's vulnerability during the Polish–Swedish wars. Polish–Swedish wars: The Polish–Swedish Wars were a series of wars between the Polish–Lithuanian Commonwealth and Sweden.
i don't know