Castle (built early 1560s) and Gifu Castle (built 1568) are known to have had the physical character of a tenshu, but are referred to in the primary record as yagura (turret, tower). Azuchi Castle is often credited as the birthplace of the tenshu. Given the earliest usages of the name, however, it seems more likely that Azuchi played a key role in linking the typology and the name. Function Unlike the other elements of Japanese castles, tenshu had little military function, but symbolised the power, wealth and extravagance of the castle's owner. Most Edo period castles were built during a period of peace lasting more than two centuries, but legends about earlier warfare suggested that once the outer defences of a castle had been breached, the defenders generally preferred to set fire to the remaining buildings and sally out to their deaths, rather than fight it out inside a fragile tenshu. Survival These structures have proved vulnerable to fire, earthquake and war. Hundreds of them were destroyed or dismantled during the final stages of the unification wars of the Sengoku period at the turn of the 17th century. Others were demolished, collapsed from neglect or were allowed to burn down during the Meiji Restoration of the 1860s. Of nineteen tenshu that survived into the 20th century, seven were destroyed during Allied air raids on Japan in the Second World War. However, several tenshu have been rebuilt in recent decades; examples are Osaka castle in 1931, Hiroshima castle in 1958 and Ōzu Castle in 2004. References The Compact Nelson Japanese-English Dictionary, Charles E. Tuttle Company, Tokyo, 1999, Kenkyusha's New Japanese-English Dictionary, Kenkyusha Limited, Tokyo, 1991, Further reading Castle architecture Castles in Japan Japanese architectural features