Volley fire

Volley fire, as a military tactic, is in its simplest form the concept of having soldiers shoot in turns. In practice, it often consists of having a line of soldiers all fire their weapons simultaneously at the enemy forces on command. This is usually to make up for the inaccuracy, slow rate of fire, and limited range of a weapon which requires extensive effort to reload. The volley fire, specifically the musketry volley technique, also known as the countermarch, requires lines of soldiers to fire on command and march back into a column to reload while the next row shoots, and so repeat fire. While this tactic is usually associated with Dutch military thinkers in the late 16th century, its principles have been applied to crossbow infantry since at least the Tang dynasty.

Although volley fire is most often associated with firearms, the concept of continuous and concerted rotating fire was practiced using crossbows since at least the Tang dynasty. During the An Lushan Rebellion the Tang general Li Guangbi successfully deployed a spear crossbow formation against the rebel cavalry forces under Shi Siming. In 756 Shi Siming raced ahead of the main army with his mounted troops to intercept Li Guangbi's Shuofang army near the town of Changshan. In response Li took Changshan in advance and set up his infantry with their backs to the town walls to prevent a sneak attack. The spearmen formed a dense defensive formation while 1000 crossbowmen divided into four sections to provide continuous volley fire. When Shi's cavalry engaged Li's Shuofang's army they were completely unable to close in on his troops and suffered heavy losses, forcing a withdrawal.

The 759 CE text Tai bai yin jing (太白陰經) by Tang military official Li Quan (李筌) contains the oldest known extant depiction and description of the volley fire technique. The Tang crossbow volley fire formation was rectangular and the illustration shows each circle as one soldier. In the front is a line labeled "shooting crossbows" (發弩) and behind that line are shorter rows of crossbowmen, two facing right and two facing left, and they are labeled "loading crossbows" (張弩). The commander (大將軍) is situated in the middle of the formation and to his right and left are vertical rows of drummers (鼓) who coordinate the firing and reloading procedure in procession: who loaded their weapons, stepped forward to the outer ranks, shot, and then retired to reload. According to Li Quan, "the classics say that the crossbow is fury. It is said that its noise is so powerful that it sounds like fury, and that's why they named it this way," and by using the volley fire method there is no end to the sound and fury, and the enemy is unable to approach. Here he is referring to the word for "crossbow" nu which is also a homophone for the word for fury nu.

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