Complex sentence: The imperial cities of Strasbourg and Hagenau joined forces against the von Berwartstein: following several weeks of futile attacks against the castle the forces succeeded in taking the castle in 1314, with the help of a traitor.
Split into simpler sentences: The imperial cities of Strasbourg and Hagenau joined forces against the von Berwartsteins. Following several weeks of futile attacks against the castle the forces succeeded in taking it in 1314, with the help of a traitor.