There is a running trope in the fantasy genre. One that says that if a character happens to be weak, they should be armed with a bow. The bow is generally defined as a speed based weapon, whereas its counterpart, the crossbow is a weapon for beefy warriors. Saddly, the relationship is actually the reverse.
During the Hundred Years War, you may be familiar with the Battles of Agincourt and Crecy, two battles said to demonstrate the supremacy of the English Warbow (more on that later, maybe). While much of the legend is pure fantasy, the fantasy does have some truth to it: the Warbow was an incredibly effective weapon. But why? And if it was so good, why did the French never use it, instead relying on mercenaries from Genoa armed with heavy crossbows known as an Arbalest?
To understand the latter, we must first understand the former. During the Middle Ages, English peasants had a long relationship with the fabled longbow. Sometimes said to originate in Wales, the longbow dominated thanks to two main properties: its range and its penetration. You see, the power of a bow generally came from two sources: its Draw Weight and its Draw Distance. Draw weight refers to the amount of force applied to the bow as it is drawn, caused by the bows inate desire to return to a lower energy state. The more prone a bow is to retaining its shape, the more it resists the bowman, increasing drawweight. Incredibly, the draw weight of an average warbow is around 150-160 lbs (according to examples found abord the Mary Rose.) Adding to that is the Draw Distance, the distance the arrow travels until the bowstring (usually made of hemp), stops pushing the arrow forward. You see, as an archer releases the bowstring, the ends of the stave begins to accelerate. This acceleration compounds the initial force of the release, accelerating the arrow until it is loose, granting the missile the power necessary to penetrate armor, even some grades of steel plate (though this was hardly normal).
So if the Warbow was so awesome and powerful, why didn't the French use it? The main reason is no one physically could. As mentioned, a standard power warbow required 150 lbs of force to achieve full draw (and some even had a draw weight of 185-200lbs the absolute peak of human physicality). And France, lacking a culture of war archers, lacked people with the conditioning to operate such mighty tools. Their solution was the Arbalest, a steel bow affixed to a wooden tiller.
As you may know, the longbow was usually made of a type of wood called yew. But a crossbow, having steel prods had a much higher draw. Light crossbows, used mostly for hunting, only had a draw weight of 400-500lbs. At this level, no human could could operate the weapon, so in this case, a crossbowman had to use a lever mechanism to span the bow. Military crossbows, however, needed to penetrate armor, not just animal hide and so had a draw weight of around 1000-1200 lbs. and had to be spanned with a rope-and-pully windlass (ideal for foot soldiers) or a gear-and-comb cranequin (a latter design that was slower but could be used on horseback)
You might be thinking, if crossbows have such a high draw weight, they must be more powerful than the measely 150lb bow. Well, as I mentioned before, bow power is based on the combination of draw wieght and draw distance, and where longbows had over an arm's length (say 2.5ft) to accelerate, an average crossbow only had 6 inches of draw. As a result, the compact nature of the crossbow required that the weapon to be extremely powerful in the draw, only to match, rather than to exceed to power of a conventional warbow.
TL;DR - For those interested in giving their characters ranged weapons, remember, a bow is a high strength weapon with power, range, and speed. The mechanical nature of a cross spanner means that, while the weapon reloads slower, it allows a much weaker individual to match the power and range without a lifetime of conditioning
+Fun fact #1: due to the fact that crossbows took longer to reload, crossbowmen carried freestanding shields called "pavices" onto the battlefield, protecting them from enemy archers
+Fun fact #2: Historical warbows are largely limited by by what a human is capable of pulling; crossbows are limited by human technologic engineering. As a result, a race that is stronger than a human (say an Orc) would likely favor bows. Not only is the design simple and the weapon quick; if the draw weight got high enough, it could match and even excede the power of a firearm...
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