The Lancastrian War was the third and final phase of the Hundred Years' War between England and France. It lasted from 1415, when Henry V of England invaded Normandy, to 1453, when the English were definitively defeated in Aquitaine. It followed a long period of peace from the end of the Caroline War in 1389. The phase is named after the House of Lancaster, the ruling house of the Kingdom of England, to which Henry V belonged. The early years of the Lancastrian War were dominated by the forces of the House of Plantagenet, who held the English throne and also claimed that of France. Initial English successes, notably at the Battle of Agincourt, coupled with divisions among the French ruling class, allowed Henry V to win the allegiance of large parts of France. Under the terms of the Treaty of Troyes of 1420, Henry V married the French princess Catherine of Valois and was made regent of the kingdom and heir to the throne of France. A victory on paper was thus achieved by the English, with their claims now having legal standing. Some of the French nobility refused to recognise the agreement, however, and so military conflict continued. Henry V and, after his death, his brother John, Duke of Bedford, brought the English to the height of their power in France, with a Plantagenet crowned in Paris.
The second half of this phase of the war was dominated by forces loyal to the House of Valois, the French-born rivals of the Plantagenets who continued to claim the throne of France themselves. Beginning in 1429, French forces counterattacked, inspired by Joan of Arc, La Hire and the Count of Dunois, and aided by a reconciliation with the Dukes of Burgundy and Brittany, who had previously sided with the Plantagenets. Charles VII was crowned in Notre-Dame de Reims in 1429, and from then a slow but steady reconquest of English-held French territories ensued. Ultimately the English would be expelled from France, except for the Pale of Calais, which would be re-captured by the French a century later. The Battle of Castillon (1453) was the final major engagement of the Hundred Years' War, but France and England remained formally at war until the Treaty of Picquigny in 1475. English, and later British, monarchs would continue to nominally claim the French throne until 1802 though they would never again seriously pursue it.
Background
In England, King Henry IV’s reign was nearing its end, marked by chronic ill health and mounting political challenges. His authority was increasingly undermined by both his failing health and growing disputes among the English nobility, including tensions with his own son, Henry of Monmouth, the future Henry V. Domestically, England was still dealing with the lingering aftereffects of the Welsh revolt led by Owain Glyndŵr, which had largely been contained by this time, though pockets of resistance remained. Rebellion and unrest among the English aristocracy persisted, fueled by dissatisfaction with the king's leadership and disputes over royal policy and succession. The king's deteriorating condition meant that Prince Henry took a more active role in government, at times even coming into open conflict with his father and the king's closest advisers.
Meanwhile, in France, the situation was even more precarious. King Charles VI continued to suffer from periods of insanity, leaving the country effectively leaderless and vulnerable. The previous decades had seen intermittent truces, dynastic disputes, and shifting alliances, but no lasting settlement to the Franco-English conflict over the French crown and territorial rights. After his father's death in 1413, Henry V assumed the throne, establishing a relatively stable political scene with a well-defined council and parliament. Trade was thriving and the country prospered. France's confrontation with England over Aquitaine had quieted due to the civil war between the Armagnacs and Burgundians. English armies were solicited for help in France, and the northern border had been quiet since the capture of James I in 1406. In this advantageous context, Henry V promptly announced his intention to assert his 'legitimate inheritance,' the crown of France.
England resumes the war
The Peace of Auxerre between the Armagnacs and the Burgundians in 1412 weakened the English's hopes of concessions, and Clarence's expedition in 1412 further cemented the Armagnacs' control of Paris. However, riots in 1413 forced John the Fearless, Duke of Burgundy to flee, leading to civil war and the Armagnacs regaining control of Paris and the government. The civil war continued through Picardy and Flanders until August 1414, when a peace agreement was reached in Arras. Both sides made overtures to Henry, hoping to enlist his help in their quarrel. Henry was content to keep them both dangling, and even suggested marrying Jean's daughter to settle the French quarrel. In January 1414, a truce was arranged between Henry and the Armagnac government in Paris to continue negotiations over Henry's claims, including the hand of Charles VI's daughter, Catherine, and a colossal dowry of a million crowns. The Armagnacs were willing to meet Henry's other demands but were not prepared to provide such a large dowry. Henry wanted war as soon as possible while the French were distracted by internal troubles. The truce was extended to August 1415, but it was merely a smoke screen for Henry's preparations.
Henry V aimed to leave a contented country behind when he ventured abroad, requiring the nobility's support. However, disaffected barons from his father's reign were vulnerable to exploiting his absence. These peers or families had been dishonoured by Henry's father when he usurped the throne from Richard II. Upon his accession, Henry V made a generous gesture to these people, ensuring their support for regaining their inheritance and not seizing the throne. He restored lands and titles to several key nobles, including the Earl of March, the grandson of the late Earl of Northumberland, and Thomas Holland. He also removed the stigma against the House of York, winning the loyalty of the Duke of York. To further solidify his rule, he elevated his own brothers, John and Humphrey, to dukedoms and made Richard Langley the Earl of Cambridge. Finally, to put the past behind him, he had the body of Richard II reburied at Westminster. Henry also aimed to leave Scotland's border secured before attacking France, holding Murdoch and James I captive, renewing the 1414 truce, and strengthening marcher castle garrisons.
Preparation
A public pronouncement regarding a potential expedition was made at Parliament in November 1414. While the lords and commons advised that there should be further negotiations with the French, they agreed that preparations for the king's expedition should be undertaken in the meantime."With whatever retinue he wished to appoint," the lay peers informed the king, they were willing to serve on his mission. It was evident from Henry's suggestions on indentures during this period that he meant for the campaign to go for at least nine months. Wages for the first quarter would be paid prior to the start of the quarter (a year was split into four periods of ninety-one days, or roughly three months). The end of the second quarter would mark the issuance of the second and third quarter pay.
The king couldn't fully prepare for war due to parliament's desire for peace negotiations. However, strategic planning on sea defense, English frontiers, and Calais was conducted in mid-February, involving experienced military men like the Duke of York, Earl of Dorset, Henry, Lord Scrope, and Sir Thomas Erpingham. However, when it was publicly known that negotiations with France had failed, military preparations for the raising of a large army moved on apace. By 1 July Henry had assembled an army of 10, 000 to 12, 000 men near Southampton.
Invasion
The French government had known for a long time that an invasion was imminent. However, Henry worked hard to keep its destination a secret. It was not to be Aquitaine, however, as the French government was not to be duped. They remembered that the same idea had been proposed by Edward III. Furthermore, his battles had demonstrated the risks associated with such an amphibious assault. Instead, there was a distinct indication of France's north coast. It could be Brittany, as English soldiers have historically preferred to land at Brest and St. Malo. Or the English monarch might follow in his ancestor's footsteps and settle close to Cherbourg. Feeling threatened, Harfleur, on the Seine estuary, quickly fortified its defenses. Some even preferred Flanders. However, the French government thought that the real invasion location was Boulogne. However, the defense-related actions were mediocre.
The Orleanists and Burgundians were divided over the call for help, with the Orleanists being lethargic and the Burgundians refusing to respond. Louis, the 19-year-old Dauphin, was appointed commander-in-chief and the Constable of France, Charles d'Albret, as his lieutenant. D'Albret collected an army at Rouen and stationed 1,500 men at Honfleur. However, the country was more concerned with heavy taxation than the invasion. The prospects for invasion were heightened when the English armada disappeared south of Bembridge. Henry V was more concerned with recovering Normandy than succouring Aquitaine. Normandy was the older patrimony of the two and had been in Anglo-Norman hands for over a century. Henry resolved to rectify the omission in the Treaty of Bretigny and made it his first objective.
Henry V, a young king, likely studied the successful campaigns of his great-grandfather and generals, particularly Henry of Lancaster and John of Gaunt. He learned from the previous wars and learned four key lessons: maintaining a successful war in distant Aquitaine, overcoming difficulties in maintaining operations on exterior lines due to communication shortcomings, occupying hostile territory with castles and fortified towns, and the importance of a firmly established base in France. The French were situated in Interior Lines, making it easier for the French to mass a large army on its borders. Additionally, France's castles and fortified towns made it nearly impossible to occupy hostile territory without a siege train. These lessons highlight the importance of a well-established base in France for successful operations. In light of these lessons and his personal desire to regain the old duchy of Normandy, he headed for the Seine estuary with Harfleur, on the north side, traditionally considered "the key to Normandy".
Harfleur
The town of Harfleur, under the command of Jean d’Estouteville, was strongly fortified and well-manned by French defenders. From the outset, Henry enforced strict discipline among his troops through a campaign ordinance that forbade looting, burning, and molesting of civilians, permitting only foraging for horses and punishing any violations with hanging. The siege of Harfleur formally began on August 18, 1415, once the town was completely isolated, and the English commenced systematic bombardment using heavy artillery while constructing siege works to encircle the town.
Despite the overwhelming strength of the English army, Henry's siege engineers did not expect a swift victory. Their concerns proved valid as early attempts to mine beneath the walls and drive trenches up to the fortifications were thwarted by flooded ditches and vigorous French countermining efforts. As a result, the English were forced to place greater reliance on their artillery barrage. This included not only gunpowder artillery but also traditional stone-throwing engines. The cast-iron guns, notable for their deafening noise and ability to hurl massive projectiles—sometimes weighing up to a quarter of a ton—were especially intimidating. Many of the stone balls were also converted into incendiaries by adding burning tar, causing further devastation within the town.
Nevertheless, the geography of Harfleur, which allowed defenders to overlook the besiegers, and frequent, determined sallies made the English artillery's task difficult. English casualties mounted due to the long-range fire of French guns and crossbows, as well as the aggressive sorties from the garrison. Despite the fierce resistance, the extended siege and continuous assault inflicted severe hardship on both the inhabitants and defenders of Harfleur. Disease, particularly dysentery, ravaged both sides, further weakening their capacity to fight. After several weeks of bombardment and repeated summons to surrender, the exhausted defenders, recognizing the hopelessness of their situation, capitulated on September 22, 1415.
Road to Agincourt
Henry V had four options to choose from: return to England, march to Bordeaux, march to Calais, or march to Rouen and Paris. He could stay at Harfleur and await reinforcements, but this was discarded due to the unhealthy air of the estuary. Paris was too risky, as it would face forces from Armagnac France and Burgundy, which would likely bring warring factions to oppose him. Bordeaux was too far away, and returning home by ship would be seen as weakness by the French and parliament. Henry sent a herald to the Dauphin at Rouen, challenging him to duel. After eight days, no reply was received, and Henry marched to Calais, leaving a strong garrison at Harfleur. Reinforcements had been received and so, notwithstanding many desertions, Henry was able to set off with an army of between six and seven thousand men on 6 October. They took with them barely sufficient rations for the next eight days, the time Henry reckoned it would take him to march to Calais.