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Castles In Ancient Japan Incorporated This Bizarre Feature To Guard Against Invading Ninjas


Many of the structures in Japan have been there for centuries. Highly skilled artisans have built many amazing castles in japan that were once home to the Japanese daimyo. When you walk through the hallways, you will hear a strange sound in the hallways and corridors. It is a type of birdsong chime that you can hear when the floorboards move when walked on. What you may not know is that there is a reason for these sounds.

Tokugawa Shogunate

From 1603 to 1868, Japan was ruled by the Tokugawa Shogunate. This was known as the Edo period. During this time, there were civil arrangements, and everyone knew their place in the social order. Emperors ruled the land, but they didn’t have very much power. Daimyo, shoguns, supported them, and lords who outnumbered the emperors by hundreds.

Orchestrated Sound

When the noblemen walked through their grand homes, they heard creaks and screeches when they walked the halls. This wasn’t the result of poor construction. There was a purpose to the sound, and it was done intentionally. The intentional sound was created by friction in the floor structure called uguisubari, which means, “bush warbler guard watch.” They were also known as nightingale floors. The floorboards were installed with movement built into the clamps. A double spike would rub against a receptor, and the friction would create a chime sound to mimic that of a nightingale’s call. This was done to alert the residents to the presence of intruders.

Telling the Difference

Since the floors would chime when a person walked on them, the guards and the staff at the palace were trained to walk across the floors in a specific pattern. This would create a deviation in the sound, so the noblemen would know if the person walking the halls belonged there or if they were an intruder.

Ancient Security System

Today, when homeowners want to protect their homes, they install home security systems. Many homeowners also install motion-activated alarm systems. When the system is armed, and the system detects motion, the alarm will go off to alert the homeowner that there is someone in the home. The sound of the alarm will often scare away the intruder, and the police will be notified. Back in the 1600s, there was no electricity and certainly no home security systems. Creating the floorboards the way they did was their own form of a motion detector home security system.


It was up to the guards to work in shifts to listen to the sounds that the floorboards were making. If they heard the sounds in an uneven and inconsistent pattern, they would know that it was someone who was trained to be in the castle walking the floors. If the chirping were consistent, the guards would suspect that there was an intruder in the palace, and the guards would be sent immediately to find the person or people who were causing the sounds and determine who they were and why they were there.


The reason that the noblemen used this ancient security system was that they were worried that someone would come and try to take over their palace. Between the 1600s and the 1800s, there was a great deal of conflict in Japan. Everyone wanted what the emperors had, and they couldn’t always trust those who were below them on the social ladder.

Who Were They Worried About?

In most cases, the emperors didn’t have to worry about the merchants, artisans, or the peasants coming to the castle trying to take control. The Samurai, Daimyos, and Soghuns were the people with the skills and the strength to take over a palace. Anyone below the Samuari didn’t have enough power to fight against the emperor’s guards. Because the Samurai, Daimyos, and the Shoguns had the knowledge and training to come into the palace without being seen, they had to use the unique floorboard design.

The invaders may have been quick enough and skilled enough to get around the place without being seen, but they couldn’t fly. This meant that they had no choice but to walk on the floor, which was the only way that they could be sure that intruders were detected before reaching the emperor’s quarters was to detect the sound when they walked. These intricate flooring systems did just that.

The Floors Remind

The people of Japan take their history very seriously; therefore, the ancient castles from the 1600s remain almost unchanged. Minor repairs have been made over time to keep the castles standing, but the floors were never changed. If you walk through the halls of these ancient castles today, you will hear the same chirping sounds heard by the guards centuries ago. Castles in ancient Japan incorporated this bizarre feature to guard against invading Ninjas, and it was genius.

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