Concentric Castle Defense System

Timeline

1. 1277–1295North Wales · GwyneddDuring the conquest of Wales, Edward I commissioned architect James of St George to build a series of concentric castles, using double or multiple rings of walls, independent inner wards and harbor supply designs to counter Welsh mountain guerrilla tactics; Caernarfon and Conwy were begun.
2. 1295–1330Beaumaris · AngleseyBeaumaris Castle, with its near-symmetric concentric square, maturely embodied the system's design logic: a wide killing ground between outer and inner curtain walls, each tower fighting independently, and a water gate securing sea supply, regarded as the crowning work of concentric castle theory.
3. 1331–1340Group of Welsh concentric castles · WalesBy the 1330s, Wales's principal concentric castles were complete and permanently garrisoned, performing military-administrative functions of suppressing rebellion, collecting tribute and controlling routes; their designs withstood small sieges and long-term logistics, becoming a firm anchor of English royal power on the frontier.
4. c. 1340–1450Western Europe · Western EuropeConcentric defense principles were widely borrowed in French fortresses of the Hundred Years' War and Iberian border castles; multiple walls, separated fields of fire between towers and independent inner wards became the textbook paradigm of late medieval fortification until the cannon revolution changed fortress logic.