Bows have existed since the the Neolithic period, used in some form by most by ancient societies. Harold II is alleged to have died with an arrow in his eye, at the battle of Hastings, as depicted on the Bayeux Tapestry.
In this period, there would be no distinction between type of bow ("longbow" as a term was invented by the Victorians). A bow would be made to fit a man's stature - 5 foot 6 inches (1.65 metres) was about the average height of a man of the period - and most bows would be what we generally now consider to be "short bows" of about 4 feet in length. In the mid-12th century, a new weapon started to come to propminence - a longer bow generally about the same height as the user, with a higher draw weight of 100 to 120 pounds. Originally from southern Wales, where records show its use from around 1150.
The first person to fully utilise the capabilities of the new weapon was probably Edward hte first, who used it in massed raks to great effect in his wars with the Scotts toward the end of the 13th century. The longbow continued to the major strategic weapon for the English for the next 300-400 years.
Later, at the battle of Agincourt (1415), sources estimate that there were about 5,000 English archers. With an individual rate of fire of 8-12 arrows a minute, up to 50,000 arrows per minute were loosed at the French for about half an hour.
Bows were long distance weapons. To protect the archers, defences had to be put in place. These usually consisted of wooden stakes, with each bowman carrying several. These would be quickly hammered in the ground in front of the bowmen. As a final defence, bowmen were armed with short swords, daggers, and mauls (leather mallets, often lead faced) used to drive the stakes. Since they were unarmoured, they were generally much faster and more manoeuvrable than armoured men.
The preferred material for "longbows" was yew, mainly from Spain and Italy (English yew is generally not suitable), though ash or elm would also be used. Most bows of the period would be "self bows", the bow being formed out of a single section from the tree, the elastic sapwood on the back of the bow, the compressible heartwood on the belly.
Some composite and recurved bows may have been brought back from the East by returning Crusaders, while the Maciejowski Bible of 1250 shows bows with recurved tiops being used almost exclusively.
For reenactment battlefield use, we generally limit bows to 35 lbs draw weight at a draw length of 28 inches. An ash selfbow for reenactment use costs in the region of £75. Arrows with rubber blunts are used (no pointy heads - they tend to kill people!), archers must be capable of an accurate high angle lob - direct fire is not used against opponents unless scripted and they are fully prepared to receive it.
Arrows must be of wood (ash, pine, or port orford cedar), authentically fletched (feathers, preferably fully bound with thread), and with self-knocks. No aluminium or carbon fibre arrows, no plastic speed flights! Genuine rubber archery blunts must be used, these must not be placed over broken or pointed tips/points.
For target shooting, authentic medieval heads may be used, but they have a tendancy to badly chew up target bosses. The Archery Centre market a late period machine made short bodkin head that is more acceptable for target use. Target arrows must still be authentically fletched.
A selection of medial arrow heads
Bibliography:
Hardy, Robert, Longbow: A Social and Military History, 1992