Tiger's mouth - Koguchi

The entrance to a castle or the enclosures that make up it. It can also be written as koguchi. There are two theories about the origin of the name: one is that the most important part of a castle resembles a tiger's fangs, so koguchi is called that, and the other is that something narrow and small is better. A castle has both defensive and offensive functions, being a place to barricade oneself in while also being a base from which to launch attacks, so koguchis were required to have both functions. Because of their importance, many ingenious designs were put into them, and they developed significantly from the latter half of the Sengoku period to the Azuchi-Momoyama period. It was also this koguchi that was the first to use stone walls. The development of koguchis can be seen from the simplest flat koguchi, to the slope koguchi on an uphill slope, the bridge koguchi and moat koguchi with a moat in front, the staggered koguchi that makes it impossible to go straight ahead, and the koguchi itself having a certain amount of space. Among these, a tiger's mouth that has a certain amount of space refers to an umadashi (horse-mouth entrance) built on the opposite bank of the moat in front of the tiger's mouth and surrounded by earthen walls, or a masugata (masugata) consisting of a square space surrounded by stone walls and two gates. These are the forms of the tiger's mouth's end. Early modern castles had multiple masugata and umadashi in addition to numerous enclosures, forming complex layouts. Furthermore, because the masugata and umadashi were designed to make detours and twists, the routes within the castle were also complex, serving to prevent enemy entry.

[Masaki Fujikawa]

"The Formation of Shokutoyo-kei Castles" by Yoshihiro Senda (2000, University of Tokyo Press)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

城郭およびそれを構成する郭(くるわ)の入り口。小口(こぐち)とも書く。名前の由来には、城郭の最も重要な部分を虎の牙に例えて虎口とした、狭く小さなものがよいので小口としたという二つの説がある。城郭には立てこもると同時に、出撃の拠点となるという防御、攻撃の両面があるため、虎口にもその二つの機能が求められた。その重要性により多くの工夫が施され、戦国期後半から織豊期にかけ著しく発達した。石垣が最初に使われたのもこの虎口である。虎口の発達は、最も単純な平虎口(ひらこぐち)から、上り坂にある坂虎口、堀を前面に設けた橋虎口や堀虎口、直進できないようにした食違い虎口、また虎口自体が一定の空間を有する虎口へととらえることができる。このうち一定の空間を有する虎口とは、虎口前堀対岸につくられ土居で囲まれた馬出(うまだし)、石垣で囲まれた方形の空間と二つの門からなる桝形(ますがた)をさす。これらが虎口の到達点の形態である。近世城郭では多数の郭に加えて、複数の桝形や馬出が設けられ複雑な縄張りを構成した。また桝形、馬出において迂回、曲折するようになっているため、城内の経路も複雑になり、敵の進入を妨げる機能を果たしている。

［藤川昌樹］

『千田嘉博著『職豊系城郭の形成』（2000・東京大学出版）』

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