For those of you who didn’t know, I shoot a longbow, I have nothing against longbows, I enjoy shooting them tremendously. However, one has to acknowledge that of all the bow designs this is the most primitive one, and yes that does matter. Many things factor into what is actually a good bow, let’s talk about that.
The Power of the Bow
There is an idea which might come from video games, movies or just people reading the draw weight, that a bigger bow is proportionally stronger. But you have to ask yourself what makes a projectile stronger. Well, essentially it’s the energy delivered on target that ultimately determines the power of a bow. What is energy? Hopefully you remember from school that kinetic energy is a function of mass and velocity, with velocity being the more important factor.
As such, what you must understand is that draw-weight =/= energy. It does not matter how big the draw weight is, if the conversation from stored spring energy to kinetic energy is inefficient. What is essential, is how fast the string moves the arrow, and for how long it does this. The higher draw weight, allows a string to move a heavier arrow at a faster or similar speed. Various materials can influence how good a similar design performs, naturally there are well made bows, and less well made bows. But the most important thing is the design of the bow. Bows were not made equally, and generally, longbows are the least efficient design, while Asian composite recurve bows are the most efficient historical designs. But nothing even compares to how efficient modern compound pulley bows are.
Below you will see a table I have created, which took, way, WAY too long to gather the data for. Consider the the column j per pound, which the table is sorted after. That is joules (energy) per pound of draw weight, and it is the best indication of energy transfer efficiency I could come up with. This kind of information is surprisingly difficult to come by with bows currently made, and not just something which is labled on the box usually, unless it’s a legal hunting bow. Some data was readily available, others I had to test or watch tests done by archers including, Armin Hirmer, Joe Gibbs, Tod Cutler and Skallagrim on YouTube who did speed tests. The * represents estimated draw length.
It should be immediately obvious, that the Chinese Manchu bow style, whether it is made of bamboo or fiberglass, is a highly efficient bow design. But it absolutely pales in comparison to the PSE Dominator compound bow. The Mary Rose longbows, are mastercrafted bows by Joe Gibbs, and you can see that even so, they are not that energy efficient, even compared to cheap mass produced bows of a Korean recurve style.
Please note that the crossbows are extremely inefficient, even with 960 pounds, the windless crossbow has less energy than even the smaller mary rose longbow. This has everything to do with draw length. European crossbow were simply extremely inefficient, and compensated for that with a huge weight.
Terminal and flight ballistics.
Energy at release is also not quite the same as energy on impact. A lot like anti tank weapons, arrows penetrate better, when they are longer. The famous length to diameter ratio is as important for an arrow as it is for an APFSDS. As you can imagine, crossbow bolts therefore are not great armour perpetrators. However, if they hit a target that isn’t covered by armour, a crossbow bolt will most likely transfer more energy quickly, potentially causing worse wounds. Additionally, crossbow bolts are more likely to get influenced by the wind and has a higher wind resistance, more quickly losing energy than arrows, and as such as less range in general.
Asian bows like the Manchu style and Mongolian bows fired very long arrows, which were also quite heavy. Asian arrows are often tanged meaning the metal tip extends into the shaft. The Manchu bows generally have a longer draw length, heavier arrows and the tang makes the shaft more rigid.
Rigidity again is important for energy transfer. The tanged arrows help in significantly increasing the energy transfer by reducing the energy wasted on arrow flexing on impact, which is quite pronounced on western arrows. Modern carbon arrows are much more rigid than any historical war arrows ever were. A compound bow doesn’t just impart more energy on the arrow, the modern arrows also transfer it better to the target due to more sophisticated construction. They can also be thinner for the same or heavier weight, allowing less air resistance again increasing energy retention.
Western vs Chinese crossbows
Chinese crossbows are profoundly different in construction from the western medieval type crossbows. From the beginning the Chinese put the trigger of the Asian crossbows on the back of the handle, rather than near the front. This meant that nearly the entire length of the Chinese crossbows is the draw length, rather than just a few inches as on the western ones. This means that Chinese crossbows are essentially just regular bows with crossbow trigger mechanisms.
Historically this has upsides and down sides. Chinese crossbows were made so that weaker people with less skill could fire bigger bows, Song dynasty crossbows were typically 100 pounds draw weight, which is quite powerful, but it is not on the level of Mary Rose or Mongolian archers at the time. Due to the self-imposed limitations of crossbow draw length in Europe, European crossbows were made with increasingly sophisticated draw assistance. In China crossbows were typically hand pulled or feet pulled, the latter required that you lay down. Obviously this is less than practical in battlefield conditions, but probably fine in a siege.
It is possible to imagine, that with a combination of technology, 900 pound steel spanned crossbow, but with a 25 inch draw length and trigger from a Chinese crossbow could be possible, which would indeed have been like a hand ballista, but no such thing was ever made.
Conclusions
Look the primary advantage of the longbow particularly in English use, was that it was cheap and available. It did the job, but it was not a spectacular weapon, and in reality it most often did not win battles. Crecy and Agincourt were the exceptions not the rules, they were victories which astounded the world, and still does today, because knights lost to these peasant weapons. If that was the case all the time, knights wouldn’t never have fought that way in general, and England would have won the 100 year war, which they did not. Longbows have been used everywhere, since basically the stone age, and they are fine weapons, but a true master archer does more than fire a heavy bow.
Some countries in history fielded archers of such epic quality, that they dominated the battlefield. No one is more famous of this than the Mongolian Empire. The Asian composite bows, were not weaker than English longbows in draw weight, but they were more energy efficient. I think it is safe to say that the Mongolian warbows of the 12th century, were stronger than the strongest warbows at Agincourt.
You might also ask why even use crossbows if they are so inefficient? Well, while European crossbows were horribly energy-inefficient compared to bows, they had several other advantages. You could use them in narrow spaces, which made them ideal for firing out of slits in castle sieges, inside houses, or heavily wooded areas in forest. You could fire them rapidly once readied, and you could reload them behind cover. They were excellent skirmishing weapons, but on an open field vs a large formation of archers, they did poorly, as shown by multiple actual European battles where this was tried. But people did use them for a reason, just not to challenge war bows on an open field.
Chinese crossbows, were not nearly has handy, mobile or versatile to use. On the other hand they allowed vast groups of peasants with minimal training, to fire reasonably powerful bows, though probably not the most powerful ones.
Either way, a master archer whether Manchu, Mongolian, Arabic or otherwise, also had the advantage of speed, being able to fire extraordinary many arrows quickly. Crossbows were horribly slow whether Chinese or Western. The master archer chose the composite bows, because they were efficient, fast, had a long range and was far more compact than a longbow. The bow was expensive and so was the archer, but if you wanted the best of the best, this is what you got, they have nothing but advantages over the alternatives and there is a reason why a small group of Mongolian master archers were able to dominate a third of the world in 2 generations, and it was not just that they had horses.