Volley fire, as a military tactic, is (in its simplest form) the concept of having soldiers shoot in the same direction en masse. In practice, it often consists of having a line of soldiers all discharge their weapons simultaneously at the enemy forces on command, known as "firing a volley", followed by more lines of soldiers repeating the same maneuver in turns. This is usually to compensate for the inaccuracy, slow rate of fire (as many early ranged weapons took a long time and much effort to reload), limited effective range and stopping power of individual weapons, which often requires a massed saturation attack to be effective. The volley fire, specifically the musketry volley technique (also known as the countermarch), requires lines of soldiers to step to the front, fire on command and then march back into a column to reload, while the next row repeats the same process.
The term "volley" came from Middle French volée, substantivation of the verb voler, which in turns came from Latin volare, both meaning "to fly", referring to the pre-firearm practice of archers mass-shooting into the air to shower their enemy with arrows. While the tactic of volley fire is usually associated with Dutch military thinkers in the late 16th century, its principles have been applied to crossbow infantry since at least the Chinese Tang dynasty.
History of crossbows
Although volley fire is most often associated with firearms, the concept of continuous and concerted rotating fire may have been practiced using crossbows since at least the Han dynasty as described in the Han-Xiongnu Wars in the Records of the Grand Historian, although it was not until the Tang dynasty that detailed illustrations appeared. 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.