If anyone needs evidence that crossbows require less training than bows, the repeating crossbow provides it. You didn't even need to fumble with bolts in mid-battle.
This East Asian development had no parallel as a one-man portable weapon. The heavier versions had parallels in some repeating bolt-firing weapons for sieges and shipboard use in ancient Mediterranean history.
The simplicity and elegance of the design is almost astonishing. Accuracy and power were poor, though. It wasn't able to exploit torsion for greater power, as the expensive late medieval hand crank heavy crossbows did.
The value of a repeating crossbow was probably in the morale effect of hundreds of bolts fired within seconds by a few dozen men, and increased by poisoned tips.
I suppose the poison didn't need to be very deadly; humans had good reasons to fear even small wounds before the introduction of penicillin. A small wound with some kind of poison - even if it's only guaranteeing an inflammation - was something to fear, and causing fear is the morale effect of weapons.
The high volume of bolts fired may also have been useful against light cavalry, as the horses could panic after sustaining several wounds and the horsemen might want to avoid getting their horses wounded like that.
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