yō no koguchi 陽の虎口

Positive castle entrance or yang entrance. A generic term for various types of castle entrance *koguchi 虎口 considered to be suitable for easy exit of outgoing sorties. Most Edo period castles built on mountain foothills *hirayamajiro 平山城, and flatland castle residences kyojō hirajiro 居城平城 had entrances belonging to this category, for example the box-shaped gate *masugata koguchi 桝形虎口 and the gate with protective barrier *umadashi koguchi 馬出虎口. These designs included a protected enclosed space or compound where troops may have gathered before going out on sorties. The term yō no koguchi is used in contrast with *in no koguchi 陰の虎口, a defensive entrance.