The repeating crossbow (Chinese: 連弩; pinyin: Lián Nŭ) is a Chinese crossbow that was invented during the Warring States period, and remained in use until the late Qing dynasty. The repeating crossbow combined the actions of spanning the bow, placing the bolt, and shooting into a one-handed movement, thus allowing for a much higher rate of fire than a normal crossbow. A top-mounted magazine containing a reservoir of bolts fed the crossbow through gravity, and the mechanism was worked by moving a rectangular lever forward and backward.
A non-recurve repeating crossbow. Ones used for war would be recurved
Ming dynasty repeating crossbow
Naval battle scroll depicting Korean soldiers utilizing a variant during the Imjin War
The Zhuge Nu is a handy little weapon that even the Confucian scholar or palace women can use in self-defence... It fires weakly so you have to tip the darts with poison. Once the darts are tipped with "tiger-killing poison", you can shoot it at a horse or a man and as long as you draw blood, your adversary will die immediately. The draw-back to the weapon is its very limited range.
According to the Wu-Yue Chunqiu (history of the Wu-Yue War), written in the Eastern Han dynasty, the repeating crossbow was invented during the Warring States Period by a Mr. Qin from the State of Chu. This is corroborated by the earliest archaeological evidence of repeating crossbows, which was excavated from a Chu burial site at Tomb 47 at Qinjiazui, Hubei Province, and has been dated to the 4th century BC, during the Warring States Period (475 - 220 BC). Unlike repeating crossbows of later eras, the ancient double shot repeating crossbow uses a pistol grip and a rear pulling mechanism for arming. The Ming repeating crossbow uses an arming mechanism which requires its user to push a rear lever upwards and downwards back and forth. Although hand held repeating crossbows were generally weak and required additional poison, probably aconite, for lethality, much larger mounted versions appeared during the Ming dynasty.
In 180 AD, Yang Xuan used a type of repeating crossbow powered by the movement of wheels:
...around A.D. 180 when Yang Xuan, Grand Protector of Lingling, attempted to suppress heavy rebel activity with badly inadequate forces. Yang's solution was to load several tens of wagons with sacks of lime and mount automatic crossbows on others. Then, deploying them into a fighting formation, he exploited the wind to engulf the enemy with clouds of lime dust, blinding them, before setting rags on the tails of the horses pulling these driverless artillery wagons alight. Directed into the enemy's heavily obscured formation, their repeating crossbows (powered by linkage with the wheels) fired repeatedly in random directions, inflicting heavy casualties. Amidst the obviously great confusion the rebels fired back furiously in self-defense, decimating each other before Yang's forces came up and largely exterminated them.
— Ralph Sawyer
The invention of the repeating crossbow has often been attributed to Zhuge Liang, but he in fact had nothing to do with it. This misconception is based on a record attributing improvements to the multiple bolt crossbows to him.
Repeating crossbows continued in use until the late Qing dynasty when it became obvious they could no longer compete with firearms.
Fired from the hip, the bolts were fired in sequence from pumping the corking lever forward and backward, arming and releasing in a continuous cyclic process until the magazine was emptied. This rocking action did not allow for precise firing, nor did the inability to sight along the barrel as in a crossbow or a modern gun.
— Liang Jieming
The basic construction of the repeating crossbow has remained very much unchanged since its invention, making it one of the longest-lived mechanical weapons. The bolts of one magazine are fired and reloaded by simply pushing and pulling the lever back and forth.
The repeating crossbow had an effective range of 70 meters and a maximum range of 180 meters. Its comparatively short range limited its usage to primarily defensive positions, where its ability to rapidly discharge 7–10 bolts in 15–20 seconds was used to prevent assaults on gates and doorways. In comparison, an arbalest could only deliver about two bolts a minute. The repeating crossbow, with its smaller and lighter ammunition, had neither the power nor the accuracy of an arbalest. Thus, it was not very useful against more heavily armoured troops unless poison was smeared on bolts, in which case even a small wound might prove fatal.