Complex sentence: He belonged to Erling Hafto, the commander of the Norwegian-crewed KNM "Thorudd", which was formerly a trawler but was converted to a minesweeper and stationed in Montrose and Dundee in Scotland.
Split into simpler sentences: He belonged to Erling Hafto, the commander of the Norwegian-crewed minesweeper KNM "Thorudd". The vessel had been converted from a former trawler and stationed in Montrose and Dundee in Scotland.