Tags: Military Structure.
Yōgaiyama Castle (要害山城 Yōgaiyama-jō) was a Sengoku period yamajiro located in Kai Province (present day Yamanashi Prefecture) constructed in the 1520s by the Takeda clan. Since 1991 its site has been proclaimed a National Historic Site by the Japanese government.Takeda Nobutora (1493-1573) secured control over Kai Province after various battles and established the center of his government at Tsutsujigasaki in what is now the city of Kōfu in 1519.
