It is said that there were a lot of castles in various parts of Japan and there were several hundred thousand castles including small forts until Ikkoku Ichijo Rei (Law of One Castle per Province) was issued in 1615.
近世の1615年に一国一城令が発布されるまでは、城は各地に多数存在し、砦のような小さなものも含めると数万城あったといわれる。