Japanese Castles 1540–1640

The principles of defence

Whatever their aesthetic appeal, Japanese castles were primarily fortresses, and the Japanese castle represented a sophisticated defence system, even if the way this operated is not always directly apparent. At first sight the graceful superstructures look flimsy and very vulnerable to fire, but they were in fact highly fire resistant, and the Japanese also lacked the means for effective artillery bombardment until quite late in their history.
One obvious disadvantage provided by the gently sloping and curved walls of the typical castle stone base was the ease with which attackers could climb them, and the way in which the unmortared blocks of stone fitted together also provided numerous handholds. One solution was the incorporation into the design of towers of the stone-dropping holes noted above which were akin to European machicolations. Unlike machicolations, however, the ishi otoshi were closed by hinged doors. An additional deterrent to would-be climbers were rows of spikes pointing downwards from certain horizontal surfaces such as is seen on the keep at Kumamoto castle and the small walls at Nagoya.

Whereas the primary consideration behind the European angle bastion was protection against artillery fire, this was only one factor taken into consideration in Japan, even though the two styles look superficially similar. In Japan an infantry attack or mining were far more likely to occur than an artillery bombardment, and it is only at the siege of Osaka in 1614/15 that anything resembling a European cannon bombardment becomes a major feature. In this case guns of European manufacture supplied the bombardment, so for this reason alone no Japanese castle can be regarded as an artillery fortress by design. There are no gun emplacements or casemates as such, and there would be few places inside Himeji, for example, where cannon could be mounted successfully. Instead the most common gunpowder weapons would be thousands of arquebuses with which an attacker or defender would sweep his opponent’s lines.
This was the technique that won the Korean castles for the invaders of 1592, an invasion army, incidentally, that took almost nothing in the way of an artillery train with it.