Task: Question Generation
Input (English): Passage: Duke Magnus Birgersson proclaiming himself king of Sweden, refused to pay the agreed sum of 6,000 marks of silver and complained about the ravages the Danish Assistance Force allegedly committed. Instead, he started a war by moving into the then Danish provinces of Halland and Skåne by total surprise in the fall of 1276.The Danes mobilized an army under marsh Uffo that stopped the Swedish army who then fled Scania. The next year Danish forces marched on Småland in retaliation for their depredations in Halland and Skåne. The Danish punitive expedition followed the scarce Swedish Defense Forces into Västergötland, where they met a Swedish part of the army of about 200 knights in armour, led by Ulf Karlsson. The Battle of Ettak was a defeat for the Danish army who were surprised in their own camp. Erik Klipping gathered a large army in 1277 and went into Västergötland which again was overcome and looted. The fortresses of Axwall and Skara was captured by the Danish army. Eric V of Denmark decided to end the campaign because it was not meant as anything other than an act of revenge in response to the Swedish king's assault on Halland and Skåne. After returning home, Eric V of Denmark began negotiations with the Swedes leading to a peace agreement in Laholm, Scania in early 1278. Magnus Birgersson had to pay war reparations which were reduced from 6,000 to 4,000 marks of silver.
Output (English): How many years did the Danish punitive expedition last?