Army Group North under Feldmarschall Wilhelm Ritter von Leeb advanced to Leningrad, its primary objective. Von Leeb's plan called for capturing the city on the move, but due to Hitler's recall of 4th Panzer Group (persuaded by his Chief of General Staff, Franz Halder, to transfer this south to participate in Fedor von Bock's push for Moscow), von Leeb had to lay the city under siege indefinitely after reaching the shores of Lake Ladoga, while trying to complete the encirclement and reaching the Finnish Army under Marshal Carl Gustaf Emil Mannerheim waiting at the Svir River, east of Leningrad. Finnish military forces were located north of Leningrad, while German forces occupied territories to the south. Both German and Finnish forces had the goal of encircling Leningrad and maintaining the blockade perimeter, thus cutting off all communication with the city and preventing the defenders from receiving any food or supplies. The Germans planned on food being their chief weapon against the citizens; German scientists had calculated that the city would reach starvation after only a few weeks.