In the fifth and sixth centuries CE, the Greek-speaking Romans systematically copied the military methods of the Huns and Avars who were ravaging Europe. One effect of this was that Roman soldiers and scholars began to write treatises on archery, and when Arabs and Turks conquered their lands they also adopted the practice of writing about archery. Because a certain YouTube video by a trick shooter (to which I will only link indirectly) has been making the rounds, I thought that it would be a good idea to post a passage from the only one of these treatises which I have to hand. This is the Strategikon of the Emperor Maurice, written within a decade or so of the year 600 (I quote from page 11 of G.T. Dennis’ translation).
The Training and Drilling of the Individual Soldier
He should be trained to shoot rapidly on foot, either in the Roman or the Persian manner. Speed is important in shaking the arrow loose and discharging it with force. That is essential and should also be practiced while mounted. In fact, even when the arrow is well aimed, shooting slowly is useless. He should practice shooting rapidly on foot from a certain distance at a spear or some other target. He should also shoot rapidly mounted on his horse at a run, to the front, the rear, the left, the right. He should practice leaping onto the horse. On horseback at the run he should fire one or two arrows rapidly and put the strung bow in its case, if it is wide enough, or a half-case designed for this purpose, and then he should grab the spear which he has been carrying on his back. With the strung bow in its case, he should hold the spear in his hand, then quickly replace it on his back, and grab the bow. It is a good idea for the soldiers to practice all this while mounted, on the march in their own country. For such exercises do not interfere with marching and do not tire out the horses.
Other, later sources explain what is meant by rapid shooting in more detail, specifying that soldiers must be able to shoot three arrows at a target at a certain distance before the first hits, or that they must be able to ride past a row of targets a few metres apart and hit them all. Some give hints about how to achieve this, such as holding arrows in the bow hand, using a bow which is lighter than the strongest bow which the archer can handle, resting the arrow on the thumb of the bow hand instead of the side, or even practicing shooting small moving targets such as dogs and birds at close range. The archer in this video has thought up other tricks, such as using a very light bow and not drawing it fully which further reduces the speed of the arrow. There were also many differences within traditions of mounted archery. Maurice later comments that the Persians shoot extremely fast but not strongly, and some peoples seem to have preferred to shoot continuously from a distance, others to gallop close and loose a few arrows before galloping to safety.
In western Europe archery traditions since the Chalcolithic have been based on long self bows, although composite bows were used occasionally from Roman times onwards and crossbows became important in the later middle ages. Europe has plenty of timber, including trees such as yew which make good bowstaves, but not grass for so many horses. Archers in these traditions practiced standing and shooting at model birds atop poles, at targets on earthen mounds some scores of yards away, or dropping arrows onto targets hundreds of yards away from above.
Archery traditions are diverse, and archers develop many different skills. When two archers from different traditions meet, each will probably each find that the other can do things which they can not. Rather than deny or dismiss, it is better to try to understand what each is trying to do and how they do it. Those interested in historical archery will find that historians and ethnologists have compiled and translated many useful sources and have advice on how to interpret pictures, stories, and other difficult kinds of evidence.
Further Reading: George T. Dennis ed. and tr., Maurice’s Strategikon (University of Pennsylvania Press: Philadelphia, 1984). David Nicolle has an encyclopedic knowledge of medieval warfare, especially that in the Moslem world, and has published many affordable books for a wide audience which describe archery techniques. On the archery of the Scots, Flemings, English, and other such peoples see the works of Roger Ascham in the sixteenth century and Hardy and Strickland, The Great Warbow.
Edit 2015/08/18: I forgot to mention the Asian Traditional Archery Research Network (ATARN), a group of bowyers, archers, and scholars who study archery from horseback and who have made many useful resources available.