Task: Question Generation
Input (English): Passage: Early in March 1676, a Danish fleet of 20 ships under Admiral Niels Juel left Copenhagen. On 29 April it landed troops on Gotland, which soon surrendered. The Swedish fleet was ordered out on 4 May, but experienced adverse winds and was delayed until 19 May. Juel had by then already left Visby, the principal port of Gotland with a garrison force. He headed for Bornholm to join with a small Danish–Dutch squadron in cruising between Scania and the island of Rügen to prevent any Swedish seaborne reinforcement from reaching Pomerania. On 25–26 May the two fleets met each another in the battle of Bornholm. Despite the considerable Swedish advantage in ships, men and guns, they were unable to inflict any losses on the allied force, and lost a fireship and two minor vessels. The battle revealed the lack of coherence and organization within the Swedish ranks, which soured relations between Creutz and his officers.After the failed action, the Swedish fleet anchored off Trelleborg where King Charles was waiting with new orders to recapture Gotland. The fleet was to avoid combat with the allies at least until they reached the northern tip of Öland, where they could fight in friendly waters. When the Swedish fleet left Trelleborg on 30 May they were soon intercepted by the allied fleet, which then began a pursuit. By this time the allies had been reinforced by another small squadron and totaled 42 vessels, with 25 large and medium ships of the line. The reinforcements brought with them a new commander, the Dutch Admiral General Cornelis Tromp, one of the most renowned naval tacticians of his time. The two fleets sailed north and on 1 June passed the northern tip of Öland in a strong gale. The Swedish ships fared poorly in the rough winds, losing masts and spars. The Swedish officers formed a battle line that held together only with great difficulty. They tried to get ahead of Tromp's ships to gain the weather gage by getting between the allies and the shore, and thereby gaining an advantageous tactical position. The Dutch ships of the allied fleet managed to sail close-hauled faster than the rest of the force and slipped between the Swedes and the coast, taking up the crucial weather gage. Later that morning the two fleets closed in on each other and were soon within firing range.
Output (English): What two fleets were involved in the Battle of Bornholm?