In 1365 the free companies, under Sir Hugh Calveley and other leaders, took service with Bertrand du Guesclin, who employed them in 1366 in compelling Peter of Castile to flee from his kingdom, and in setting up his bastard brother, Henry of Trastámara, as king in his stead.
Peter, who was in alliance with Edward III, sent messengers to Prince Edward asking his help, and on receiving a gracious answer at Corunna, set out at once, and arrived at Bayonne with his son and his three daughters.
The prince met him at Capbreton, and rode with him to Bordeaux.

Many of the prince's lords, both English and Gascon, were unwilling that he should espouse Peter's cause, but he declared that it was not fitting that a bastard should inherit a kingdom, or drive out his lawfully born brother, and that no king or king's son ought to suffer such disrespect to royalty; nor could any turn him from his determination to restore the king.

Peter won friends by declaring that he would make Edward's son king of Galicia, and would divide his riches among those who helped him.
A parliament was held at Bordeaux, in which it was decided to ask the wishes of the English king.
Edward replied that it was right that his son should help Peter, and the prince held another parliament at which the king's letter was read.
Then the lords agreed to give their help, provided that their pay was secured to them.
In order to give them the required security, the prince agreed to lend Peter whatever money was necessary.

The prince and Peter then held a conference with Charles of Navarre at Bayonne, and agreed with him to allow their troops to pass through his dominions.
In order to persuade him to do this, Peter had, besides other grants, to pay him 56,000 florins, and this sum was lent him by the prince.
On 23 September a series of agreements were entered into between the prince, Peter, and Charles of Navarre, at Libourne, on the Dordogne, by which Peter covenanted to put the prince in possession of the province of Biscay and the territory and fortress of Castro de Urdialès as pledges for the repayment of this debt, to pay 550,000 florins for six months' wages at specified dates, 250,000 florins being the prince's wages, and 800,000 florins the wages of the lords who were to serve in the expedition.
He consented to leave his three daughters in the prince's hands as hostages for the fulfilment of these terms, and further agreed that whenever the king, the prince, or their heirs, the king of England, should march in person against the Moors, they should have the command of the vanguard before all other Christian kings, and that if they were not present the banner of the king of England should be carried in the vanguard side by side with the banner of Castile.

The prince received a hundred thousand francs from his father out of the ransom of John II, the late king of France, and broke up his plate to help to pay the soldiers he was taking into his pay.
While his army was assembling he remained at Angoulême, and was there visited by Peter.
He then stayed over Christmas at Bordeaux, where his wife, Joan, gave birth to their second son Richard (the next king of England).

Prince Edward left Bordeaux early in February 1367, and joined his army at Dax, where he remained three days, and received a reinforcement of four hundred men-at-arms and four hundred archers sent out by his father under his brother John, duke of Lancaster.
From Dax the prince advanced via Saint-Jean-Pied-de-Port through Roncesvalles (in the Pyrenees) to Pamplona (the capital of Kingdom of Navarre).

When Calveley and other English and Gascon leaders of free companies found that Prince Edward was about to fight for Peter, they withdrew from the service of Henry of Trastámara, and joined Prince Edward "because he was their natural lord".
While the prince was at Pamplona he received a letter of defiance from Henry.

From Pamplona the prince marched by Arruiz to Salvatierra, which opened its gates to his army, and thence advanced to Vitoria, intending to march on Burgos by this direct route.
A body of his knight
In 1365 the free companies, under Sir Hugh Calveley and other leaders, took service with Bertrand du Guesclin, who employed them in 1366 in compelling Peter of Castile to flee from his kingdom, and in setting up his bastard brother, Henry of Trastámara, as king in his stead. Peter, who was in alliance with Edward III, sent messengers to Prince Edward asking his help, and on receiving a gracious answer at Corunna, set out at once, and arrived at Bayonne with his son and his three daughters. The prince met him at Capbreton, and rode with him to Bordeaux.
Many of the prince's lords, both English and Gascon, were unwilling that he should espouse Peter's cause, but he declared that it was not fitting that a bastard should inherit a kingdom, or drive out his lawfully born brother, and that no king or king's son ought to suffer such disrespect to royalty; nor could any turn him from his determination to restore the king.
Peter won friends by declaring that he would make Edward's son king of Galicia, and would divide his riches among those who helped him. A parliament was held at Bordeaux, in which it was decided to ask the wishes of the English king. Edward replied that it was right that his son should help Peter, and the prince held another parliament at which the king's letter was read. Then the lords agreed to give their help, provided that their pay was secured to them. In order to give them the required security, the prince agreed to lend Peter whatever money was necessary.
The prince and Peter then held a conference with Charles of Navarre at Bayonne, and agreed with him to allow their troops to pass through his dominions. In order to persuade him to do this, Peter had, besides other grants, to pay him 56,000 florins, and this sum was lent him by the prince. On 23 September a series of agreements were entered into between the prince, Peter, and Charles of Navarre, at Libourne, on the Dordogne, by which Peter covenanted to put the prince in possession of the province of Biscay and the territory and fortress of Castro de Urdialès as pledges for the repayment of this debt, to pay 550,000 florins for six months' wages at specified dates, 250,000 florins being the prince's wages, and 800,000 florins the wages of the lords who were to serve in the expedition. He consented to leave his three daughters in the prince's hands as hostages for the fulfilment of these terms, and further agreed that whenever the king, the prince, or their heirs, the king of England, should march in person against the Moors, they should have the command of the vanguard before all other Christian kings, and that if they were not present the banner of the king of England should be carried in the vanguard side by side with the banner of Castile.
The prince received a hundred thousand francs from his father out of the ransom of John II, the late king of France, and broke up his plate to help to pay the soldiers he was taking into his pay. While his army was assembling he remained at Angoulême, and was there visited by Peter. He then stayed over Christmas at Bordeaux, where his wife, Joan, gave birth to their second son Richard (the next king of England).
Prince Edward left Bordeaux early in February 1367, and joined his army at Dax, where he remained three days, and received a reinforcement of four hundred men-at-arms and four hundred archers sent out by his father under his brother John, duke of Lancaster. From Dax the prince advanced via Saint-Jean-Pied-de-Port through Roncesvalles (in the Pyrenees) to Pamplona (the capital of Kingdom of Navarre).
When Calveley and other English and Gascon leaders of free companies found that Prince Edward was about to fight for Peter, they withdrew from the service of Henry of Trastámara, and joined Prince Edward "because he was their natural lord". While the prince was at Pamplona he received a letter of defiance from Henry.
From Pamplona the prince marched by Arruiz to Salvatierra, which opened its gates to his army, and thence advanced to Vitoria, intending to march on Burgos by this direct route. A body of his knight
Edward the Black Prince