Fortress

19th century

During the 18th century, it was found that the continuous enceinte, or main defensive enclosure of a bastion fortress, could not be made large enough to accommodate the enormous field armies which were increasingly being employed in Europe; neither could the defenses be constructed far enough away from the fortress town to protect the inhabitants from bombardment by the besiegers, the range of whose guns was steadily increasing as better manufactured weapons were introduced. Therefore, since refortifying the Prussian fortress cities of Koblenz and Köln after 1815, the principle of the ring fortress or girdle fortress was used: forts, each several hundred meters out from the original enceinte, were carefully sited so as to make best use of the terrain and to be capable of mutual support with neighboring forts. Gone were citadels surrounding towns: forts were to be moved some distance away from cities to keep the enemy at a distance so their artillery could not bombard said urbanized settlements. From now on a ring of forts were to be built at a spacing that would allow them to effectively cover the intervals between them.