Torstenson War The Torstenson war , Hannibal controversy or Hannibal War ( ) was a short period of conflict between Sweden and Denmark – Norway which occurred in 1643 to 1645 during the waning days of the Thirty Years ' War . The names refer to Swedish general Lennart Torstenson and Norwegian governor - general Hannibal Sehested . Denmark , who had already withdrawn from the Thirty Years ' War by the Treaty of Lübeck in 1629 , suffered a major defeat . In the Second Treaty of Brömsebro ( 1645 ) , which concluded the war , Denmark had to make huge territorial concessions and exempt Sweden from the Sound Dues , " de facto " acknowledging the end of the Danish " dominium maris baltici " . Danish efforts to reverse this result in the Second Northern , Scanian and Great Northern wars were unsuccessful . Background . Sweden had been highly successful in the Thirty Years ' War , having defeated Imperial armies in Germany and seen substantial victories under Gustavus Adolphus and , after his death , under the leadership of Count Axel Oxenstierna , Lord High Chancellor of Sweden . At the same time , Sweden was continually threatened by Denmark – Norway , which almost completely encircled Sweden from the south ( Blekinge , Scania , and Halland ) , the west ( Bohuslän ) and the northwest ( Jämtland ) . The Danish Sound Dues were also a continuing source of irritation and a contributing factor to the war . In the spring of 1643 the Swedish Privy Council determined that their military strength made territorial gains at the expense of Denmark likely . The Count drew up the plan for war and directed a surprise multiple - front attack on Denmark in May . Beginning . Swedish Field Marshal Lennart Torstensson was ordered to march against Denmark . Proceeding from Moravia , his forces entered Danish territory at Holstein on 12 December and by the end of January 1644 the Jutland peninsula was in his possession . In February 1644 the Swedish General Gustav Horn occupied much of the then Danish provinces of Halland and Scania , except for the Danish fortress town of Malmø , with an army of 11 , 000 men . Responses . Denmark . This attack caught Denmark unaware and poorly prepared , but King Christian IV retained his presence of mind . He placed his confidence in the fleet to protect the home islands , just winning the Battle of Colberger Heide on 1 July 1644 but suffering a decisive defeat in the Battle of Fehmarn on 13 October 1644 against a Dutch – Swedish fleet . He also counted on the forces of Norway to relieve the pressures on Danish provinces in Scania by attacking Sweden along the Norwegian - Swedish border . Norway . Norway , which was then governed by Christian ' s son - in - law , Governor - General Hannibal Sehested , was a reluctant participant . The Norwegian populace opposed an attack on Sweden , correctly suspecting that an attack on Sweden would only leave them open to counterattack . Their opposition to Statholder Sehested ’ s direction grew bitter , and the war was lampooned as the " Hannibal war . " The Danes cared little for Norwegian public sentiment when Denmark itself was seriously threatened , and Jacob Ulfeld initiated an attack into Sweden from Norwegian Jemtland . He was driven back out of Sweden and Swedish troops temporarily occupied Jemtland as well as advancing into the Norwegian Østerdal before being driven back . Sehested had made preparations to advance with his own army and a similar army under Henrik Bjelke into Swedish Värmland , but was ordered to relieve the King in the Danish attack on Gothenburg . Upon the arrival of Sehested the King joined his fleet and performed heroically , even though wounded , preventing Torstensson ’ s army from moving onto the Danish islands . On the Norwegian front , Sehested attacked the newly founded Swedish city of Vänersborg and destroyed it . He also sent Norwegian troops under the command of George von Reichwein across the border from Vinger and Eidskog as well as troops under Henrik Bjelke into Swedish Dalsland . Denouement . Christian ’ s Danish forces were so exhausted that he was forced to accept the mediation of France and the United Provinces in suing for peace ; and to sign the Peace of Brömsebro on 13 August 1645 , a humiliating disaster to Denmark – Norway . The Swedes had achieved much from their surprise attack on Denmark . They were exempted from the Sound Dues , the toll for passing through Danish territory into the Baltic Sea . Denmark – Norway ceded to Sweden the Norwegian provinces of Jemtland , Herjedalen and Idre & Serna and the strategically located Danish islands of Gotland in the center of the Baltic and Øsel in the Baltic Sea . Further , Sweden occupied the Danish province of Halland as well as other territories for 30 years as a guarantee of these provisions . The Peace also included the Danish heir to the throne , Frederick II , Administrator of the Prince - Bishopric of Verden ( 1634 – 1645 ) and of the Prince - Archbishopric of Bremen ( 1635 – 1645 ) , who had to resign , with the two prince - bishoprics being occupied by the Swedes . According to the Peace of Westphalia both prince - bishoprics became a fief of the Holy Roman Empire to the Swedish crown in 1648 . Long - term consequences . The defeat of Denmark reversed the historic balance of power in the Baltic . Sweden now virtually controlled the Baltic , had unrestricted access to the North Sea and was no longer encircled by Denmark – Norway . As importantly , the successful surprise attack assured that Denmark – Norway now looked for an opportunity to recoup their losses , while Sweden looked for opportunities to expand further , setting the stage for continued conflict on the Baltic over the next century .