Henry's ragged no-hope army was largely made up of volunteers and vassals, most of them sick with dysentery and exhausted from a summer-long campaign in miserable weather. Harried and hopelessly outnumbered, they prepared to face the flower of French nobility a few miles from Agincourt. The French army, under King Charles VI's commander, Constable D'Albert, numbered in excess of twenty thousand men, mostly knights. Opposing them, King Henry V commanded around six thousand ragged and starving men-but, of those, five thousand were archers, and most of them Welsh.

On that bright Saint Crispin's day in October, the great French army was massacred. Accounts of the battle read like a "What Not To Do" handbook of combat. The French produced blunder after blunder in bewildering array, so many as to be almost literally incredible. Even so, it would have taken a military miracle for French horse-mounted knights to succeed when, by some estimates, upwards of seventy-two thousand arrows were loosed in the first fateful minute of the conflict. Of this devastating power, historian Philip Warner writes, "Fear of the longbow swept through France. Its deadly long-range destruction made it seem an almost supernatural weapon." Prayers against it were offered in churches at the time; this was a last resort, for nothing else came close to stopping it.

Britain's losses that day in the fields of Agincourt numbered around one hundred-and many of those were noncombatants: unarmed, defenceless baggage boys and chaplains who were slaughtered out of extreme frustration by the already-beaten French who attacked the supply wagons encamped a mile or so from the battle field. On the other side of the equation, the French lost around two thousand counts, barons, and dukes; well over three thousand knights and men-at-arms; and more than one thousand common soldiers for a tally in excess of six thousand dead. These numbers are conservative: some accounts of the time estimate that as many as twelve thousand were killed or captured that day.

In any event, it was a defeat so devastating that it would be a generation or more before France could regain its military confidence against the British. As military historian Sir Charles Oman put it: "That unarmoured men should prevail against men cased with mail and plate on plain, open ground was reckoned one of the marvels of the age."

Decisive as it may have been, Agincourt was not by a very long shot the first battle to be decided by the longbow, nor would it be the last. But it was, perhaps, the most powerful demonstration of a now little-remembered law of medieval combat-namely, that when two opposing forces met, those with the most archers would invariably win. A sort of corollary stated that when both sides boasted roughly the same number of archers, the side with the most Welsh archers would win. Such was the highly recognized talent of the Cymry with the longbow, and their renowned fighting spirit.

As we are once again reminded by the British chronicle of the Saxon kings, the Brenhinedd y Saesson: "The men of Brycheiniog and the men of Gwent and the men of Gwynllwg rebelled against the oppression of the Ffreinc. And then the Ffreinc moved their host into Gwent; and they gained no profit thereby, but many were slain in the place called Celli Garnant. Thereupon, soon after that, they went with their host into Brycheiniog, and they gained no profit thereby, but they were slain by the sons of Idnerth ap Cadwgan, namely, Gruffydd and Ifor…"

This rebellion provoked a reaction: "In that year King William Rufus mustered a host past number against the Cymry. But the Cymry trusted in God with their prayers and fastings and alms and penances and placed their hope in God. And they harassed their foes so that the Ffreinc dared not go into the woods or the wild places, but traversed the open lands sorely fatigued, and thence returned home empty-handed. And thus the Cymry defended their land with joy."

It was precisely this fierce and tenacious spirit that the Normans faced in their ill-advised invasion of Wales. The unrivalled talent with the longbow-though born in the forests and valleys of Wales-was honed to lethal perfection in the white heat of contention following William II's decision to extend the dubious benefits of his reign beyond the March. It was a decision which sparked a conflict that was to sputter and flare for the next two hundred years or more, and provided the fertile ground from which sprang the legends featuring that shrewd archer, Robin Hood.

Wily Welsh archers were not the only plague in William's life, however; he also suffered from that acute affliction of his time: fear of purgatory.

Like a great many prominent men,William Rufus found himself in continual debt to the church, paying out huge sums of money for prayers to be said for the departed under his purview. All throughout the Middle Ages, abbeys and monasteries large and small did a roaring trade in penitential prayer, employing their priests on a perpetual, round-the-clock basis. The holy brothers prayed for their patrons and their patrons' families, of course, and also for the souls of those unfortunates their patrons might have killed. For the right fee, the local abbot could guarantee that the requisite time in purgatory would be shortened, or even excused altogether, and no one would have to suffer eternal damnation.

Quaint as it might seem today, buying and selling prayers for cash was a business conducted in dead earnest at the time. For it would be difficult to overestimate the fear of hell and its attendant horrors for the medieval mind. As tangible proof of this deep-seated and widespread phobia, the abbeys rose stone by ornately carved stone to dominate the medieval landscape of Europe. These beautifully wrought works of art can still be visited a thousand years later: belief made physically manifest.

Though greatly reduced in every way now, all through the Middle Ages the monasteries amassed enormous wealth on the exchange of prayer for silver, becoming ever more powerful, extending their influence into all areas of medieval life and commerce. It was to be their downfall in the end. For when the wealth and power grew so massive as to exceed that of the monarchy, the threatened kings fought back.

For William II, bucking the trend was not an option. He was caught in the stifling embrace of a system he could neither control nor ignore. He was not the last monarch to discover that the need for money to pay his debt to the church would intrude on, if not dictate, his political agenda. Decisions of polity often bowed before the expediency of keeping the clergy cheerful-even in weightier matters such as war and peace. The medieval king might not like it, but more often than not he swallowed his resentment and did what was necessary to pay up. Whoever said heaven would come cheap?

Keep Reading for an Excerpt of The Paradise War, Book One in the Song of Albion Trilogy