Japanese castles, or jō, emerged from simple wooden stockades into fortified complexes of wood and stone by the 16th century. Though their foundations and walls often used unmortared stones—piled as a sloping base called ishigaki—the superstructures remained chiefly timber, with plastered walls and elaborate tile roofs. This blend of flexibility and fire risk meant many original keeps burned or were dismantled over centuries, even as stone walls endured. Early castles, known as yamajirō (“mountain castles”), were carved directly into hilltops. Builders cleared timber, dug moats fed by diverted streams, and cut trenches to slow attackers. Wooden palisades and thatch-roofed halls sat atop these earthworks, but erosion and fire limits soon drove a shift to flatland and hill-base sites, where stout stone foundations could support grander buildings. By the Sengoku era, jō had become the power centers and residences of daimyō. Oda Nobunaga’s Azuchi Castle (1576) introduced the tenshu — a multi-storied main keep that combined storehouse, watchtower and symbol of authority. Its stone base, soaring wooden superstructure and lavish interiors set the template for Hideyoshi’s Osaka Castle and Ieyasu’s Edo Castle, both designed to awe rivals as much as to defend. Castles incorporated every element of the landscape into defense: layered baileys, high yagura turrets, narrow gateways and winding paths that exposed attackers to archers and arquebusiers. Tiled roofs and plastered walls resisted fire better than thatch, while inward-sloping ishigaki made scaling walls nearly impossible. Yet even “unconquerable” keeps fell to prolonged siege or political decree, and by the Meiji era most were ordered dismantled. Today over a hundred jō survive—some, like Matsue and Kōchi, in near-original form; others, like Hiroshima, carefully reconstructed. Their stonework, tenshu silhouettes and gatehouses remain potent symbols of feudal Japan, preserved as museums and World Heritage sites that showcase the fusion of military ingenuity and aesthetic refinement that defined the castle age.

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Momoyama Castle