Schanze

A schanze is, according to the specialist terminology of German fortification construction, an independent fieldwork, that is frequently used in the construction of temporary field fortifications. The word is German and has no direct English equivalent, although the word sconce is derived from Dutch schans, which is cognate to the German word.

In everyday German speech, however, it is commonplace to refer to permanent fortifications as schanzen, because in many places in times of war, fieldworks that were only temporarily thrown up were later turned into permanent fortifications.

Source: Wikipedia