As the scale of battles became larger, the importance of Koguchi increased, and much care was given to the design and location of moats, earthworks and stone walls to enhance the defensive capability of castle walls.
合戦が大規模になってくるとさらに虎口の重要性は増し、城郭の防衛力向上のため、堀、土塁、石垣の配置に工夫が施されるようになる。