The campaign that began in June 1674 and ended with his death in July 1675 has been described as 'Turenne's most brilliant.' Despite being out-numbered, he attacked Bournonville on 4 October before he could be reinforced; although the Battle of Entzheim was indecisive, the Imperials withdrew, entering winter quarters around Colmar, where they were joined by Frederick William's troops. Although it was normal practice to avoid campaigning during the winter, Turenne went on the offensive. He marched south, using the Vosges mountains to screen his movements from the Imperial commanders and reached Belfort on 27 December (see Map).