"Zwinger" (German pronunciation: [ˈt͡svɪŋɐ]) is a German word for outer ward or outer bailey. It represents an open kill zone area between two defensive walls that is used for defensive purposes. Zwingers were built in the post-classical and early modern periods to improve the defence of castles and town walls. The term is usually left untranslated, but is sometimes rendered as "outer courtyard", presumably referring to the subsequent role of a Zwinger as a castle's defences became redundant and it was converted into a palace or schloss; however, this belies its original purpose as a form of killing ground for the defence. The word is linked with zwingen, "to force", perhaps because the Zwinger forced an enemy to negotiate it before assaulting the main defensive line. Essenwein states that