The Nihonmatsu Castle Honmaru
A Japanese castle’s honmaru is its main compound, surrounded by walls and designed to be defended against the fiercest attack. In most castles, the honmaru contained a towering keep called a tenshu as well as other buildings used for living quarters, domain administration, and storage. When a battle went against the castle’s defenders, the honmaru was where they gathered to mount their final defense. If the enemy breached the honmaru, the battle was lost.
The stone walls around the honmaru during the Niwa family’s tenure have been excavated and restored to give a sense of what the compound was like during its heyday. Because the honmaru occupied the high ground for greater defensibility, today its former site doubles as a lookout point with panoramic views of the city to the east and the Adatara massif to the west.
The Missing Keep
The northern corner of Nihonmatsu Castle’s honmaru contains a raised square area called the tenshudai, or “keep foundation.” Historians had long assumed that the keep that stood here had been destroyed when the castle burned in 1868, but careful archaeological work eventually revealed that a building was never constructed on the site.
Why Nihonmatsu Castle had a keep foundation but no keep is unclear, but the most likely explanation is political. By the time the lords of the castle had the funds to build a keep on top of the foundation, there was no plausible threat to defend against, and the Tokugawa shogunate saw no need to allow the domain to increase its military capabilities and enable a possible rebellion.
Defending the Gate
The only entrance to Nihonmatsu Castle’s honmaru was the southern gate, which has now been restored to its former state. As in most castles of the time, the gate opened onto an enclosure with a hard right turn and a second gate before the honmaru proper. This was designed to make the gate more defensible by preventing potential attackers from charging in, and the enclosure also made a useful staging ground when defenders were preparing to charge out.