Japanese castle defense tricks, Tonashi "no door" gate

As I wrote before, I am fascinated by the inventive builders of the Japanese castles, and the defensive tricks they used to protect against sieges. In this photo taken at the Matsuyama castle, you can see right next to the large and heavily defended main gate a smaller gate, called tonashi (meaning "no door") which doesn't even have closing doors.

It had a cunning purpose, because hurried attackers, while trying to advance as quickly as possible, were certain to rush through such a tempting gate. But once they were passing through it, they were reaching a deadly trap, a closed, cramped and heavily defended area.