The Battle of Poitiers
The Hundred Years War, which actually lasted 116 years, is famous for the fact that it is remembered for three primary engagements, each of which resulted in a decisive English victory, and still in the end England lost the war. Today is the anniversary of the first of those engagements, the Battle of Poitiers fought in 1356. The other two battles were Crecy in 1346 and Agincourt in 1415.
Poitiers is the outlier among these three; it did not involve an attempted uphill charge of the French against a prepared line of English archers, men at arms and other infantry. In addition it involved an important contribution by an English calvary force. But there the dissimilarities end. The French, while significantly outnumbering the English forces, were again hampered by poor chain of command. And the final casualty count was far in favor of the English.
The English forces, which included a significant contingent from the French province of Gascony, were led by Edward the Black Prince, son of Edward III and heir apparent (the throne would go eventually to Richard III, son of the Black Prince and heir presumptive while his father lived). At that time Gascony was the remaining remnant in France of the Angevin Empire assembled by Henry II and Eleanor of Aquitain; Bordeaux its capital was larger than London. A dispute over Gascony was the impetus for the Hundred Years War.
The Black Prince and many of the force that had fought at Crecy were there as Poitiers loomed; they knew what lay ahead. In October, 1355 they began a chevauchée (think Sherman's March to the Sea) through Southern France, then returning to Gascony. Over the winter and into the spring of 1356 numerous towns were captured with some nobles switching their alliance to the English. Meanwhile in that summer another English army invaded Normandy and did significant damage to French property and alliances.
In August of 1356 the English/Gascon forse set out north and then north-east in another chevauchee some 50 miles wide, described by David Green as “deliberately destructive, extremely brutal ... methodical and sophisticated." The Black Prince at 51. Meanwhile the French King John continued to focus on unsuccessful seige operations in Normandy, attempting without success to dislodge dug-in English forces at Breteuil, a venture described by Sumption as "a pointless endeavour". Jonathan Sumption, Trial by Fire. The Hundred Years' War (Vol II) at 224. Eventually he convinced the English garrison to abandon Breteuil with safe passage, an agreement they could take with them their loot and treasure, and a substantial additional payment (a/k/a a bribe). Only then did the French army, buttressed by some 200 Scotsman, move against Edward’s forces, they now each maneuvering for an advantageous field of battle. Meanwhile a French force of maybe 700 was ambushed by the English with some 240 killed or captured. At that point King John turned to make battle while the forces of the Black Prince picked and fortified with stakes and trenches a position from which they, unmounted, would answer a French assault.
After fruitless negotiations for English safe passage back to Gascony a French army of some 15,000 (maybe 11,000 men at arms, 2000 light infantry and 2000 crossbow men). organized against the English/Gascon army of maybe 6,000 (3000 men at arms, 2000 bowmen and 1000 Gascon light infantry). At dawn on September 19 the French organized some 500 yards in front of the English’ prepared position, but they did not advance for some two hours. The battle began with French mounted forces attacking the bowmen arrayed on the two flanks. On one side they were hampered by a swamp the horses could not traverse. While many of the horses were protected from arrow fire by armor on their chests and heads, their hindquarters were not protected, and a continent of archers moved so they could shoot at the unprotected areas. The first French assault fell largely to the English longbow, although hand-to-hand combat on the English right flank was an important contributor to repulsing that onslaught.
And then came the second French attack of some 4000 men at arms, an often hand-to-hand battle that waged for two hours. Here the flexibility of the English/Gascon forces proved vital; while the French may be praised for following their orders the English and Gascon proved flexible in responding to threatened breakthroughs; Green in his Battle of Poiters (pp. 52-53) commended "an extremely flexible tactical response" while Hoskins in In the Steps of the Black Prince: The Road to Poitiers, 1355–1356 (p. 192) observed that having fought together since 1355 the Black Prince's army was disciplined as a unit. Eventually the contingent fighting with the dauphin (the French heir apparent) and two of his brothers retreated, which it seems all the French forces took as a signal to disengage. From the French perspective the timing might not have been more disadvantageous; at that point all English reserves were committed.
A lackluster third attack had no real bearing on the battle, while the fourth, comprised of maybe 4000 men at arms, some fresh and some survivors of an earlier wave, around the French king John, marched at the English position with the French national banner, the Oriflamme unfurled - under it all French were forbidden to take prisoners; all combat was to the death.
While the details are debated, the English took a two prong approach to this now forth onslaught. First, a group of unknown size mounted their horses, rode around the flank, and from the rear attacked the French forces. At the same time, the main body, led by the Black Prince, moved forward from their secured position, advancing on the main French body. Eventually the French force collapsed and disintegrated. The bearer of the Oriflamne was killed and that national banner captured as was, eventually, King John himself and his son Philip.
While casualty figures are notoriously difficult to ascertain, the French likely lost 2500 men-at-arms, and an equal number of other soldiers. Meanwhile, the English likely lost 40 men-at-arms and an unknown number of infantry and bowmen.
The Black Prince’s army retreated to Gascony with the French king in hand. After several fits and starts including a treaty providing for John’s ransom that the dauphin rejected as too costly, John was freed in return for the French transferring to the English significant territory in France and a ransom of 3 million ecu (the 1360 Treaty of Bretigny).
David Green’s The Black Prince (2011) is a good resource, as is Peter Hoskin’svSteps of the Black Prince: The Road to Poitiers, 1355–1356 (also 2011). Still, Jonathan Sumption’s monumental five volume history of the Hundred Years War (The Hundred Years War I – Trial by Battle; The Hundred Years War II – Trial by Fire; The Hundred Years War III – Divided Houses;The Hundred Years War IV – Cursed Kings; and The Hundred Years War V - Triumph and Illusion) is without a bout the definitive treatment.