Gates

Castle designers saw the gates as the weak points in a castle's defensive system. Therefore, much care was taken to ensure the integrity of each gate, and to ensure the harmony of all the gates as a whole. The gates were laid out in such a fashion as to confuse and mislead the enemy away from the tenshu. The gates closest to the tenshu were also smaller and stronger, thus restricting the flow of invaders who made it all the way.

Castle gates (also called mon) come in two major varieties. The first kind are called usume mon, meaning "embedded gate"; these were built directly into the walls of the castle. The other kind are built from plaster and wood, much like tenshu and yagura. While all gates were constructed of wood, larger gates were often reinforced by plating them with iron.

The main gate to a castle is called the ote mon. Besides its obvious defensive role, the ote mon had a symbolic role as well; like the tenshu, the ote mon was a symbol of a daimyo's influence and wealth. They were meant not only to stop invaders but to intimidate them as well.

Masugata

Masugata were very effective defensive structures. They are usually found at key points of entry to the castle, such as at the main entrance and at moat crossings. A masugata is a high-walled, rectangular courtyard with two gates--one leading into the castle and the other to the outside. The gate leading to the outside is small and usually connected to a bridge. This is so that invading armies could only enter a few men at a time, thus taking away any advantage that greater numbers might have given them. Once inside the masugata, the invaders were subject to attack from castle troops lining the high walls. While under fire, the invading force would then have to breach the inner gate in order to advance into the castle.

Breaking through the inner gate was no easy task. To begin with, it was positioned at a right angle to the outer gate; this made it virtually impossible to simply charge through the masugata with a battering ram. Furthermore, the inner gate was usually a heavily guarded yagura-mon, so breaking through would have been a challenge even without the heavy barrage of gunfire and arrows from above.