Pact with Pedro I of Castile and war with Aragon, 1362. Navarre, a European kingdom, not only shaped the history of France during this reign, it also played an important role in the peninsula. Behind it were Castile and Aragon. In the former, Pedro I and his brother Enrique de Trastamara waged a bloody war that continued to splash the Pyrenean kingdom; in 1362, Pedro allied himself with Edward II of England (Treaty of London), his brother Enrique achieved an alliance with the French, thus involving the peninsula in the Hundred Years' War (1339-1453). On the other hand, his other royal colleague, Pedro IV the Ceremonious of Aragon, was engaged in a "atrocious struggle" (Raynaldo) with the Castilian monarch "where Don Carlos, who moved them, could not abstain from the bloody lawsuit. He practiced the policy of agreements, insincerely agreed with whichever of the two dangerous neighbors pressed him the most at the moment. He wanted to preserve the freedom of his arms, but sometimes circumstances overcame the intention (Campin: Navarra in its ..., p. 251)". On May 22, 1362, the representatives of Castile -Iigo Ortiz de las Cuevas and Gil Velázquez- and those of Navarre -Arnalt Remon de Agramont and Ramiro de Arellano- met in Estella and before Don Carlos agreed as Yanguas expresses: That both kings were friends of friends and enemies of enemies; that if the king of Navarre were captured in his kingdom or outside it, in the lordship of Aragon or in any other lands within twenty leagues around Navarre, or his person besieged, or there were to be battle against another king or enemy, or a city besieged, or if his subjects rose up against him or were rebellious, the king of Castile would be obliged to go with his body and with all his power and at his own expense to help Don Carlos. That if any of the above-mentioned things happened in Normandy or in France, the king of Castile would send the king of Navarre as much help as he could by sea and by land at his own expense for four months, three of service and one of departure; and that if more were needed, the king of Navarre would pay the expense, as he paid his natives, the Castilian people then following to the aid of Navarre as much as was necessary. That if the king of Navarre were to wage war with the king of Aragon or another person, the king of Castile should also wage war against the enemies of Navarre with all his power. That the Castilian should allow the troops of Navarre to pass through his land to make war on his enemies, paying for the provisions they took, but that only the leaders of the army should enter the towns with 50 men on horseback and another 50 on foot, leaving the rest camped; that in their transit through places and bridges, they should only do so in companies of 200 men, without the latter passing until the former had done so. That if the war were in Normandy, except in the cases d, the king of Castile should send 1,500 men on foot in his own ships for four months. That if any enemy of Navarre crossed into Castile he should be seized and handed over to King Charles so that he could do as he pleased. That in any war in which King Peter helped Charles, the latter could not make peace or a truce without the advice of that monarch. And the King of Navarre was obliged, for his part, to do the same with respect to Castile. This agreement was ratified on June 2 by Peter I in Carrascosa. Consequently, on the 14th the King of Navarre d war on the King of Aragon. In July Salvatierra de Aragon was besieged and fell into Navarrese hands, as well as Ruesta.