Bows and arrows have been around since Paleolithic times, with evidence of them as early as 8000-9000 BC in Germany. http://www.newarchaeology.com/articles/history_bow_and_arrows.php
Kennewick man, the controversial skeleton found in the banks of the Columbia River inKennewick,Washington dates to roughly 7500 BC. A CT scan revealed a stone, projectile point embedded in his hip.
Oetzi the Iceman was found with a quiver of arrows with flint heads and an unfinished yew longbow–taller than he was–in his pack. He dates to 3300 BC.
The confirmed first use of the longbow was in 633 AD, in a battle between the Welsh, led by Cadwallon ap Cadfan of Gwynedd, against the Northumbrians. (Though I haven’t been able to find the original source that confirms this). http://www.themiddleages.net/longbow.html
The shot killed Ofrid (or Osric?), son of Edwin of Northumbria, who just happened to be Cadwallon’s foster-uncle. Cadwallon had allied himself with Penda of Mercia in an attempt to drive the Northumbrians from Gwynedd, after Edwin had defeated his father and taken over the country. Cadwallon was successful. http://www.earlybritishkingdoms.com/bios/cadwagd.html
Saxons, as a rule, were not archers. It is another five centuries before there is any recorded use of a longbow in England. The men of Wales used longbows against the Normans, from the moment they arrived to conquer England and Wales, up through the death of Llywelyn ap Gruffydd. One of the greatest victories for Llywelyn was in 1257 before the Battle of Cymerau where the Normans lost 3000 men (http://www.sarahwoodbury.com/cymerau/). At Llandeilo Fawr, they cowered for two days under a hail of arrows from the Welsh.
Starting 1252 in England, the longbow was finally accepted as a formal military weapon. “In 1252 the Assize of Arms required that all landowning yeomen with an annual income between 40 to a 100 shillings were to be armed and trained with a longbow (war bow) and the more wealthy yeomen were also required to possess a sword, buckler, dagger and to be trained in their use.” http://robinhode.webs.com/yeomen.htm
“C.1280: Longbow adopted by Edward I during the Welsh campaigns after seeing how effectively the Welsh used the bow.
1331-1333: Longbow used by Edward III during the Scottish Campaign.
1337-1453b: The hundred years war with France:During this time, the English and Welsh longbowmen were the most prominent part of the English army, sometimes outnumbering the Men-at-Arms by as much as 10:1. The average was a ratio of about 3:1.” http://www.archers.org/default.asp?section=History&page=longbow
What is it about the longbow that is both effective and also prevented its earlier adaptation? This has to do with 1) it’s size, and 2) the length of time required to learn its use.
The standard yew longbow was over 6 feet long (6 ft. 6 inches), with a yard long arrow. They are powerful weapons that require enormous strength to draw. In general, the draw weight is 120-150 pounds, with a range between 200 and 300 yards. “In battle, longbow formations fired 10-12 volleys per minute. Each archer was provided 60-72 arrows. A force of 4,000 longbowmen could loose 240,000 arrows within the space of five minutes.” http://www.militaryhistory.teamultimedia.com/History%20of%20Weapons/Welsh%20and%20English%20Longbow.html
Thus, in order to master its use, a man must practice. A lot. Once King Edward of Englandrealized the longbow’s full potential, he adopted it from the Welsh, such that “To ensure a steady stream of bowmen for his army, Edward I banned all sports except archery on Sundays. Shooting ranges were set up on or near church property so parishioners would follow worship services with archery practice.” http://www.militaryhistory.teamultimedia.com/History%20of%20Weapons/Welsh%20and%20English%20Longbow.html
Edward III used the long bow to great effect during the Hundred Years War, filling his ranks with Welsh and English longbowmen that decimated the French ranks, particularly at the Battles of Crecy and Agincourt. http://en.wikipedia.org/wiki/English_longbow