MINOR UPDATE JUNE 10, 2025
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| Scale model of a Sui Dynasty capital warship equipped with six V-shape Pai Gan. Source: Wikimedia Commons. |
Pai Gan was first recorded in use during an uprising against Western Jin
Dynasty led by
Du Tao (杜弢) in 311 A.D. and quickly grew in popularity in the subsequent dynasties.
Before long, this potent weapon had become one of the most common naval
weapons in China, so much so specialised warships designed to use Pai Gan as
their primary armament became a staple in various Chinese navies and were given
descriptive names such as Pai Jian (拍艦, lit.'Swatting ship') and
Jin Chi Jian (金翅艦, lit. 'Golden wings ship', likely named after raised Pai Gan mounted at the port and starboard of said ship). Pai Gan gradually fell out of popularity after Song period due to the advent of firearms, although it continued to see limited use during Ming period.
Theoretical operation
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| Illustration of a Lou Chuan (樓舡), or tower ship, from 'Wu Jing Zong Yao (《武經總要》)'. Historians are yet undecided about whether the crane-like device mounted on the top of the ship is an indigenous form of counterweight trebuchet or a Pai Gan. |
Although the exact nature of this weapon is unclear, written records describe Pai Gan as being similar to a ship's mast, as well as compare it to a Jie Gao (桔槔), a.k.a. shadoof. In fact, the weapon was simply called Jie Gao initially before acquiring a more specific name to distinguish it from the irrigation tool. Pai Gan had a short range, and was seemingly a one-off weapon or at least took a very long time before it could be used again. This led to the development of countermeasure tactics such as sending out small boats to bait enemy ships into activating their Pai Gan prematurely.
There are ongoing debates on the exact workings of Pai Gan. Some see Pai Gan as nothing more than a ship-mounted traction trebuchet, while others imagine Pai Gan as a boulder tied to a crane arm, intended to be used as a giant striking hammer. Currently, the striking hammer interpretation seem to be the dominant view, with researchers proposing several candidate designs for Pai Gan, although each comes with their own pros and cons. The first candidate, a "T-shape" Pai Gan, most closely resembles a Jie Gao/shadoof, but has abysmal reach and is mechanically inefficient, not to mention its hammer has a high chance of smashing into the ship it is mounted on. On the other hand, the second candidate, a "V-shape" Pai Gan, operates on a similar principle as Greek Sambuca and Roman Corvus which is far more mechanically sound, although this design certainly does not evoke the image of a Jie Gan/shadoof.
Personally, I lean heavily towards the view that Pai Gan was simply a trebuchet, as there is at least one record mentioning Pai Gan being used to attack shore fortifications.I believe that with some tweaks to the "T-shape" Pai Gan—namely mounting the arm on a much shorter pole and having it face inwards, as well as arranging it so that the arm must be manually pulled rather than simply released—it can easily be turned into a functioning stone-thrower while still matching the available written descriptions. Better yet, my proposed Pai Gan does not preclude the striking-hammer interpretation and will in fact resolve all the issues present in both the "T-shape" and "V-shape" versions while being more stable and powerful than either.
