Complex sentence: At the end of June, heavy Danish surveillance of the Gothenburg archipelago had been arranged; a force consisting of four ships and four galleys had been placed between Klåver island and Tjuvkil.
Split into simpler sentences: At the end of June, heavy Danish surveillance of the Gothenburg archipelago had been arranged. A force consisting of four ships and four galleys had been placed between Klåver island and Tjuvkil.