Defensive structures were a feature of urban areas in German-speaking Europe. Systems of walls, fortresses, moats and other defensive structures shaped urban life for centuries. The walled fortresses had the function of containing military force. They limited the population centers to an urban core within the fortifications and restricted the space in which housing, trade and other activities could take place. However, this map shows the process of "defortification", i.e. the removal of these walls and defenses and the transformation of military into urban spaces. Note the rapid acceleration of defortification after 1789.