Treatise on Armament Technology, Volume 114

Military Equipment: Defense of Fortifications

...depends on the size of the structure. If the fort is large, there should be many; if the fort is small, there should be fewer. Generally, the empty space between two towers must not exceed fifty paces Approximately 75 meters or 250 feet; this ensures overlapping fields of fire.. Furthermore, in cases where a fort has corners that project outward or sections that recede inward, one must assess the terrain to position the towers so they can support each other.

Currently, builders only construct a single tower on each side, regardless of the distance or whether the wall projects or recedes. Even if arrows and stones original: 矢石 shishi, a general term for all non-gunpowder projectiles. can reach the target, they are weak and lack force. In an instant, the enemy original: 虜 lu, a derogatory term for invaders, typically referring to Mongol or Manchu forces in this period. will seize the advantage.

Moreover, the towers are built to the same height as the walls, and the top platform measures less than ten feet original: 丈 zhang, approximately 3.3 meters. across. The reason wall parapets original: 陴 pi, the low protective walls or battlements atop a fortification. are so often brought down by the enemy is that when the wall is low, stones can easily reach them. If the tower is no higher than the wall, then the tower's own parapets are likewise difficult to protect. If the top platform is only ten feet wide, how many men can it possibly hold? How can they find the space to deploy their arrows and firearms?

Furthermore, if the tower parapets number fewer than five or six, the enemy can focus the fire of two bows on a single opening. This makes the men on the tower afraid to even poke their heads out to look, which is the same as having no tower at all. These are all major defects. Current regulations state the height of a tower should be three...