A report on Concentric castle, Castle and Siege

A concentric castle is a castle with two or more concentric curtain walls, such that the outer wall is lower than the inner and can be defended from it.

Historians (in particular Hugh Kennedy) have argued that the concentric defence arose as a response to advances in siege technology in the crusader states from the 12th to the 13th century.

These changes in defence have been attributed to a mixture of castle technology from the Crusades, such as concentric fortification, and inspiration from earlier defences, such as Roman forts.

In particular, medieval fortifications became progressively stronger—for example, the advent of the concentric castle from the period of the Crusades—and more dangerous to attackers—witness the increasing use of machicolations and murder-holes, as well the preparation of hot or incendiary substances.

In the European Middle Ages, virtually all large cities had city walls—Dubrovnik in Dalmatia is a well-preserved example—and more important cities had citadels, forts, or castles.

Although primitive, they were often effective, and were only overcome by the extensive use of siege engines and other siege warfare techniques, such as at the Battle of Alesia.