But if Isabella was guilty of these revolting crimes, she was speedily punished. Her youngest son, Charles, who now became Dauphin, though but sixteen, was extremely artful, and by no means disposed to yield to the domination of his mother, whom he as heartily despised as his elder brothers had done. Isabella herself was arrested and sent into close confinement at Tours. The Count of Armagnac is said to have the more willingly executed this severity on Isabella because she had violently complained of his seizure of her treasures both at Paris and Mélun, a measure to which the public necessities had driven him.

Enraged to frenzy by the loss of her favourite, of her power, and of her money, Isabella now meditated deep revenge. She had hated the Duke of Burgundy with a mortal hatred ever since he assassinated her beloved Duke of Orleans; and he had now added to his offences by implicating her in a manner in the murder of her own son, the Dauphin John. Yet the very next thing which the public heard was that Isabella had escaped from her prison at Tours, and thrown herself into the arms of the Duke of Burgundy, her old and most detested enemy. Such are the terrible extremes of a bad woman's vengeance. She now burned, at any cost, to revenge herself on Armagnac, and not less so on her own son Charles, whose destruction she sought as earnestly as she had done that of his brothers. This most unnatural woman had bribed her keepers to allow her to attend early mass at the church of Marmontier, in the suburbs of Tours. They accompanied her, but suddenly found themselves surprised by the Duke of Burgundy, who had secreted himself for the purpose in a neighbouring forest, with 800 men-at-arms. The moment Isabella was in the guardianship of this prince, she proclaimed herself regent of the kingdom during the continuance of the king's malady, and the Duke of Burgundy her lieutenant.

Such was the position of affairs in France at the moment that Henry V. of England landed at Honfleur, on the coast of Normandy, on the 14th of August, 1417, with 16,000 men-at-arms, an equal number of archers, and a long train of artillery, and other military engines, attended by an efficient body of sappers, miners, carpenters, and other artificers, and a fleet of 1,500 ships. Two years had elapsed since the fatal battle of Agincourt; yet the infatuated princes of France, though they knew that Henry never had his eyes off their country, but was constantly employed in planning its subjugation, had taken no measures whatever for its defence. On the contrary, they had spent the time in mutual destruction, and in doing all in their power to exhaust its strength, and demoralise the people. They appeared given up by an indignant Providence to the destroying force of their own base passions, a nation of suicidal monsters rather than of men; and while Henry of England was landing on their coasts with his invading army, the Duke of Burgundy was in full march on Paris, accompanied by the queen, breathing vengeance on the Armagnacs.

Burgundy, after the sudden death of the Dauphin, had besieged that city with an army of 60,000 cavalry. He promised to restore peace and abolish all oppressive taxes. The people in the country were ready to look upon him as a deliverer; and many cities, including Amiens, Abbeville, Dourlens, Montreuil, and other towns in Picardy opened their gates to him. Paris, in the hands of the Armagnacs, made a steadfast resistance. He, however, became master of Châlons, Troyes, Auxerre, and on being joined by Isabella, most of the towns, except those taken by the King of England, declared for Burgundy and the queen. Isabella had a great seal engraved, and appointed her officers of state. She declared that the Armagnacs held the king and Dauphin prisoners in Paris, and were, therefore, traitors. She made Burgundy governor-general of the whole kingdom, appointed the Duke of Lorraine constable, and the Prince of Orange governor of Languedoc. There was a great flocking of princes and nobility to the queen's court, and thus there were established two royal parties and two courts, the one with the king and Dauphin in Paris, the other with the queen at Chartres. The people, elated by the promises of Burgundy, rose in many places and killed the tax-gatherers, crying, "Long live Burgundy, and no taxes!" They regarded every rich man as an Armagnac, for that was a good plea on which to plunder him; and thus passed the winter of 1417.

Meantime, Henry of England advanced into the heart of Normandy, having, on setting out, issued to his army orders in consonance with those enlightened principles of humanity and policy which he had adopted in such noble contrast to the practice of the Edwards. He forbade, on pain of the severest punishment, all breaches of discipline, all injury to the lives and property of the peaceable inhabitants, and especially all insult to clergymen, or outrage to the wives, widows, and maidens of the country. Yet the Normans, neglected by their own rulers, who were engaged like wolves in tearing each others' throats instead of defending their common soil, still retained their allegiance, and regarding Henry, not as the descendant of their ancient dukes, but as a foreign invader, rejected him with great bravery. Probably the atrocities committed on them by the Edwards had thoroughly alienated their hearts from the English. But they were unable to contend with the superior forces and martial skill of Henry; Caen resisted, but was taken by assault; Bayeux submitted voluntarily; and l'Aigle, Lisieux, Alençon, and Falaise, after some stout resistance. Henry then went into comfortable winter quarters, intending to proceed, on the return of spring, with his proposed task of reducing every fortress in Normandy.

While Henry was thus successfully prosecuting his campaign in Normandy, there had occurred a slight disturbance at home. The Scots, thinking that, the king being absent with the flower of the army, the kingdom must be left greatly unprotected, made a descent upon England. The Duke of Albany and Earl Douglas crossed the borders each with an army, and while Albany laid siege to the castle of Berwick, Douglas invested that of Roxburgh. But the Dukes of Exeter and Bedford, the regent, made a rapid march northward with such forces that the Scottish leaders suddenly abandoned their enterprise, and disbanded their armies.

Simultaneously with this inroad once more appeared Sir John Oldcastle, Lord Cobham, on the scene. He had been concealed in Wales, but the absence of the king afforded him also the expectation of taking vengeance on his enemies. It had been surmised that the Scots and Sir John had mutually concerted this attack. Be this, however, as it may, there can be no doubt that both Sir John and the Lollards in general were greatly embittered by the cruelties practised on them by the bishops. These dignitaries had set them the example of bloodshed, and had certainly taken the initiative in the attempt to put down difference of theological opinion by destroying their opponents, and during the three years that Lord Cobham had eluded them, they had pursued and burnt the Lollards with increasing severity. Such lessons are readily taught, and nothing could be more natural than that the injured party should seek retaliation in kind. Sir John, too, was probably deeply incensed by his old companion, the king, giving him over so forcibly to the tender mercies of the clergy; and, though they could not in this case assert that he sought his life, he probably felt little compunction in disturbing his Government in the endeavour to come at the official persecutors.

The hasty retreat of the Scots defeated the intentions of the Lollards, and Lord Cobham, hastening from his rendezvous near St. Albans, endeavoured to regain the Welsh mountains, but he was intercepted near Broniart, in Montgomeryshire, by the retainers of Sir Edward Charlton, Earl of Powis. When brought before the House of Peers, his former indictment was read, and he was asked by the Duke of Bedford what he had to say in his defence. He had begun a bold and able speech in reply, but being stopped and desired to give a direct answer, he refused to plead, declaring that there was no authority in that court so long as Richard II. was alive in Scotland; for, like many others, he was of opinion that the Scottish Richard was genuine. He was at once condemned, and was hanged as a traitor in St. Giles's Fields, and burnt as a heretic, December, 1417.

In the spring of 1418 Henry resumed his operations in Normandy with vigour. He had received a reinforcement of 15,000 men, so that he could divide his troops, and conduct several operations at the same time. The Dukes of Gloucester and Clarence, the king's brothers, took the command of different bodies of men, and proceeded to reduce the strongest towns in Lower Normandy. Gloucester compelled Cherbourg to surrender, after a long and obstinate defence, on the 29th of September; but before this most of the towns of Lower Normandy had opened their gates. Henry advanced along the Seine and made himself master of the whole country from Louviers to the sea; finding, in this part of his campaign, infinite advantage from his conquest of Harfleur. Pont de l'Arche completed the possession of all Lower Normandy, with the exception of Cherbourg, which Gloucester was blockading. By July, making certain of the ultimate fall of this city, Henry regarded Lower Normandy as his own. Before proceeding to the siege of Rouen, he organised a Government for Lower Normandy, appointed a chancellor and treasurer, and left that part of France, though under foreign rule, far quieter and more habitable than any other district of the realm.