When at last Werth reappeared in the field it was as general of cavalry in the Imperial and Bavarian and Cologne services. His first campaign against the French marshal Guebriant was uneventful, but his second (1643) in which Baron Franz von Mercy was his commander-in-chief, was the Battle of Tuttlingen in which Werth was instrumental in a surprise victory. In 1644 he was in the lower Rhine country, but he returned to Mercy's headquarters in time to fight in the Battle of Freiburg. In the following year he played a decisive role in the Second Battle of Nördlingen. Mercy was killed in this action, and Werth temporarily commanded the defeated arm until succeeded by Field-marshal Geleen. Werth was disappointed, but remained thoroughly loyal to his soldierly code of honour, and found an outlet for his anger in renewed military activity.