Baltic Sea. That's the reason. Peter was trying very hard to establish a foothold on its banks. If you look at the map of the Scandinavian peninsula you'll see that the only naval trade route was from Archangelsk which meant moving in the extreme north around the peninsula to mainland Europe. Russia had no ports in the Baltic sea and Sweden ruled these waters. Karl XII was trying to ban Peter's access to the Baltic Sea in this war. St. Petersburg is Russia's 'window' to Europe exactly because of that - the shortest naval way to Europe starts there.Originally Posted by Hanna