The early medieval period was marked by motte-and-bailey castles which were mostly made from wood. The motte-and-bailey castles proved very effective military fortifications but they had the serious drawback of being prone to fire due to their wooden construction.
This and other requirements evolved the early medieval castle designs and by the late 12th century, new kinds of castles were being erected all over Europe. These can essentially be categorised as high to late medieval period castles. Such castles were built from stone, included many new design elements, were typically larger in size, and were far more formidable in terms of military fortifications.
Until the 12th century, the timber castles survived alongside the stone castles. But by the late 12th century, medieval castles were increasingly being built with stone. This was necessitated by a number of factors. The primary reason for the decline in the popularity of early medieval motte-and-bailey castles was their wooden construction.
Such construction wasn’t durable and was more vulnerable during an attack. As a result, stone emerged as a more useful and durable ingredient for castle-building. With the increasingly widespread use of stone, the lords who commissioned the building of castles envisioned newer designs. The exposure of European regions to each other and outside attackers also significantly contributed to the evolution of late medieval castles.
From the 12th century onwards, medieval castles were typically more elaborate in their outlook and more militarily formidable. Nearly all notable castles from the 12th century to the end of the medieval period were made in stone. By the 12th century, the design of stone castles included the use of a great keep and the towers flanking the external curtain wall.
These innovations contributed to the subsequent 13th-century innovations in design. By the 13th century, different European regions had been exposed to the Crusading efforts and had also withstood different other attackers. Such military experience led to the evolution of concentric designs of castles.
Concentric castles were one of the most notable design developments in later medieval castles and had walls within walls to provide extra defensive capabilities.
Concentric castles were first constructed in different parts of Europe by notable Crusader Military Orders such as the Teutonic Knights and the Knights Templar. These Orders effectively used such castles as a defence against different attackers, especially Islamic forces.
Concentric castles are typically comprised of multiple rings of walls surrounding a circular inner keep. Each inner wall was higher to help the defenders from all walls attack the enemies. Between each wall was a brief space where the defenders could attack the invaders even if they breached the outer wall.
Each wall was further fortified by linking with a number of towers, greatly augmenting the defences of a castle. Concentric castles proved very effective in military terms and were highly defensible.
Edward I of England had been on the Crusades and observed such castles during his Crusading period. He borrowed the concept and implemented it in his campaigns in the region of Wales, effectively cementing his control of Wales with such secure castles during the 13th century.