The idea of the nunchaku may bring up images of a screaming Bruce Lee wannabe devastating a half dozen overweight gangsters in shirts so ugly they deserved the beating from the moment they walked on the screen.
But the word flail only brings to mind the back-breaking work of peasants threshing grain. The nunchaku seems made for combat, the flail, for labor.
First I should mention that the flail I speak of is the uneven staff, one section at least twice the length of the other, hooked together with chain and often dotted with nails or spikes. Known by a number of names such as LianJia (flail) or Big Sweeper, this is now a much less-frequently seen Kung Fu demonstration weapon than the joined twin sticks we presently call the Nunchaku.
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As the pressure built up to modernize and renovate Kung Fu in the 20th century, certain weapons were stored in the closet. Primary among these were instruments that the elite considered to be crude or inconsequential because they represented the poorer, pre-modern China, the one that they wanted to eliminate. The flail, almost always been associated with farmers, suffered reduced status. But it is wrong to assume that this farm implement made it way into warfare by accident.
Noisy, unruly, deceptively simple looking, the flail can be explored in five minutes but might take a lifetime to perfect. Originally developed with two sticks and probably a leather strap, the flail is considerably longer on one side than the other so the user need not bend over for long hours while threshing.
Admittedly a farm implement, it was adapted to warfare quite early. Actually there is evidence of widespread use of the flail in battle as far back as the Song dynasty (960-1276). The instrument itself is traceable more than a thousand years before that but it may have been employed “unofficially” in battle even earlier than the Song.
A useful tool for husking grain it was given the name “flail” before the Tang dynasty ( 618-907) and employed in some civil defense strategies.
One record states: “The flail was used as though it were threshing, with the women striking the men outside the walls.” This simple phrase “as though it were threshing” informs us that the military weapon had emerged from the farm implement, not from some specialized tool.
This also shows two important aspects of the flail and why the city women could employ it. The first is that the flail, like advanced Kung Fu weapons such as the dart and steel whip, have a certain element of randomness to them which the expert controls to his advantage, once he possesses the skill. You see this even today with the long tassel swords, a seemingly gentle weapon which, if it is in an ornery mood, can wreck a master’s otherwise stellar performance. In the case of civil defense, teaching the city women a single move like ‘thrust’. coupled with the random dance of the short head section, would actually increase their chances of an effective blow.
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That leads to the second bit of evidence that these weapons were used against scaling soldiers probably trying to breach the wall with ladders and poles, and you have a good picture of the flail’s function. We even have a precedent in that women, such as Lady Kung, became famous for their long pole work employed in exactly the same manner. When martial artists today see the ten plus foot pole work from a woman martial artist they should realize that this was even tougher in the old days, performed from the crenels of some stone wall and leaning over to boot.
When the flail is mentioned in reference to warfare, again we see it used against mounted fighters. Certainly the overwhelming danger of the Song period was the mounted Mongol warrior. 
The most famous response to this seemingly unstoppable attacker was the invention by Yue Fei, the great Chinese folk hero, who developed the shield and saber defense that caused the horse to slip off the shield dropping itself and its rider into the range of the short saber. People in Kung Fu still practice the shield and saber combined form. But another option would be the flail. Its jumping front section would obviously work against a horse’s legs or a rider’s head with equal efficacy. If the pole were long enough it might actually be better than the spear for limited use of toppling a rider or crippling a mount.
Of course, modifications developed. The Essential Military Classic records the use of the Iron Wolf Tooth flail for civil defense, an adaptation that paralleled pretty closely the design of the flail in Europe. At that point in history the instrument, now a full fledged weapon, became was known as the “Crafty” flail. Some flails, possibly inspired by tribesmen encountered by Chinese troops themselves, did not even have a short head but simply ended in a length chain that could wrap and catch an antagonist.
Being a Shaolin practitioner myself, I play the Big Sweeper, as I like to call it. When you first pick it up it seems harmless and, compared to the three sectional staff, a little remedial. Most martial artists are familiar with the story that the three sectional was a favorite staff of the Emperor Zhao Kuang Yin (who became the Taizu emperor of the Song). The legend says that this favorite weapon of his was cut into three pieces during battle but Zhao loved it so much he had it clasped together with chain and sleeve. Then, during battle, it was able to wrap around a shield and surprise the wielder with its increased velocity. I loved the story and was fascinated by the weapon but never believed that it would be that effective in battle. The Big Sweeper is different. You can still thrust with the longer stick, the torque created is incredible, it is so random it would be almost impossible to block.
You have to know what you are doing. It has its traps. For instance, if you bring it back too quickly it would just as soon smash your hand as the enemy’s. The short head is truly uncontrollable most of the time and you have to learn how to predict and conform to the possibilities.
Some teachers say that weapons such as the short stick and the nunchaku are effective for close quarters but are not generally taught in Kung Fu because there is very little to teach. A short weapon, according to principle, is simply an extension of the hand. I don’t know. The nunchaku does no doubt require skill, but the challenge of mastering the Big Sweeper might even beat that.
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Resources:
VCD from Western Staff style
Thanks for the brief introduction to the threshing flail. I learned nunchaku from my sifu who regarded it as a grappling weapon and remedial physical therapy device for soft tissue shoulder injuries.
Certainly this is a bit of village martial arts that needs to be explored.