Complex sentence: In 1814, Van Halen decided to change sides, forging the signature of Marshal Louis-Gabriel Suchet in documents advising the French commanders of various fortresses to surrender because the war was over.
Split into simpler sentences: In 1814, Van Halen decided to change to the opposing army. By forging the signature of Marshal Louis-Gabriel Suchet, French commanders were advised to surrender of various fortresses because the documents claimed that war was over.