Defensive castle compounds in no kuruwa 陰の郭 and offensive castle compounds yō no kuruwa 陽の郭. In Chinese, yin and yang compounds. Such in and yō concepts were applied to castle design by early modern period military scholars (17th-19th centuries). Defensive compounds are located at the rear of a castle, whereas offensive compounds are at the front, allowing castle garrisons to go on the attack easily. These principles also affected the design of installations such as bridges and gateway barriers *umadashi 馬出.
The same distinction between defensive and offensive orientation was also applied to entire castles: a castle designed to be primarily defensive was known as in no nawa 陰の縄 or in no shiro 陰の城; a castle designed to be used for attacking was called yō no nawa 陽の縄 or yō no shiro 陽の城.