Nagoya Castle Keeps, Nagoya

Nagoya Castle is known for its distinctive linked-keep design, in which the five-story main keep is connected to a smaller keep by a fortified passageway. Evidence suggests that another smaller keep may originally have been planned on the western side of the main keep. Traces of an opening in the upper section of the stone foundation appear to mark the intended entrance to this unbuilt structure. During construction, however, the connecting entrance was moved to its present position.

The keeps also served practical military purposes. The lower level of the main keep was used to store weapons and other supplies, while highly flammable materials such as gunpowder were kept in separate facilities to reduce the danger of fire. Both the main and smaller keeps were destroyed during the air raids of 1945 and reconstructed in 1959 using steel-reinforced concrete while reproducing their historic exterior appearance.

The castle’s extensive stone walls were constructed through the combined efforts of 20 feudal lords ordered to participate in the project. Katō Kiyomasa, a celebrated castle builder, was responsible for the stone foundation beneath the main keep. Many stones bear engraved symbols identifying the lords or work groups responsible for transporting and placing them. These marks helped prevent disputes over building materials and remain visible in several parts of the castle.

The stone foundation beneath the keep employs a technique known as ōgi kōbai, or “fan-shaped slope.” Its walls rise steeply and then curve outward near the top, creating a profile resembling an open fan. Often associated with Katō Kiyomasa, this construction method helped distribute pressure within the wall while making the upper section difficult for attackers to climb.

Between the main and smaller keeps is a roofless, fortified passage enclosed by earthen and stone walls. Along part of its western side, rows of iron spikes known as shinobi-gaeshi, or “climber repellers,” were installed beneath the eaves to prevent enemy soldiers from scaling the walls. These details illustrate how even the connecting spaces and rooflines were designed to obstruct intruders and strengthen the defenses of the castle’s central enclosure.