Rubuta ci gaba don wannan sakin layi - Saboda ƙiyayya ga Napoleon, Sarkin Sweden Gustav IV Adolf ya yi yaƙi da Faransa - akasin shawarar masu ba shi shawara - kuma ya shiga Yaƙin Ƙungiyar ta Uku, a ranar 31 ga Oktoba 1805; bayan da ya kasance mai tsaka tsaki na shekaru da yawa tun bayan abubuwan da suka faru na juyin juya halin Faransa. Shekarar farko ta yaƙi ta zama babban abin takaici ga 'yan Sweden, kamar yadda sarki na Sweden ya yi ƙoƙari ne kawai don ci gaba da matsayinsa, haɗe da nasarori da yawa ga abokansa
Ka yi haƙuri. An sake samun koma baya a ƙarshen 1806, a lokacin Yaƙin Ƙungiyar ta huɗu, yayin da aka tilasta wa sojojin Sweden 1,000 da ba su da makamai a cikin yaƙin Lübeck, yayin da aka kama su a cikin hanyar jigilar kaya zuwa Stralsund. A farkon 1807, yayin da 'yan Sweden a karkashin Hans Henric von Essen suka kasance cikin Pomerania na Sweden, sojojin Faransa a karkashin Édouard Mortier sun ketare iyakar Sweden tare da mutane 12,000, kuma daga baya suka fara toshewar Stralsund a ranar 30 ga Janairu, bayan wasu juriya na Sweden. Yaren mutanen Sweden suna da kimanin mutane 13,000 a Stralsund da kuma tsibirin Rügen mai muhimmanci, ciki har da Landwehr na mutane 3,000.