From Imperial Spain: 1469-1716, by J. H. Elliott (Penguin, 2002), 2nd ed., Kindle Loc. 981-1014:
The traditional hostility of Castile and Portugal, exacerbated by Portuguese intervention in the question of the Castilian succession, provided an added incentive to Castile to acquire its own possessions overseas. One of the major battlefields in the Castilian-Portuguese conflict of the fifteenth century was to be the Canary Islands, which seem to have been discovered by the Genoese in the early fourteenth century. During the course of the Castilian War of Succession Ferdinand and Isabella attempted to substantiate their rights to the Canaries by dispatching an expedition from Seville in 1478 to occupy the Grand Canary. The resistance of the islanders and dissensions among the Castilians frustrated the intentions of Ferdinand and Isabella, and it was only in 1482 that a new expedition under Alfonso Fernández de Lugo laid the foundations for eventual success, beginning with the subjugation of Grand Canary in the following year. Even now, Palma was not taken till 1492 and Tenerife till 1493. But, in the meantime, the treaty of 1479 ending the war between Castile and Portugal had settled the dispute over the Canaries to Castile’s advantage. Portugal renounced its claim to the Canaries in return for a recognition of her exclusive right to Guinea, the kingdom of Fez, Madeira, and the Azores, and so Castile acquired its first overseas possessions.
Castile’s occupation of the Canaries was an event of major importance in the history of its overseas expansion. Their geographical position was to make them of exceptional value as an indispensable staging-post on the route to America: all Columbus’s four expeditions put in at the Canary archipelago. But they were also to provide the perfect laboratory for Castile’s colonial experiments, serving as the natural link between the Reconquista in Spain and the conquest of America.
In the conquest and colonization of the Canaries can be seen at once the continuation and extension of techniques already well tried in the later Middle Ages, and the forging of new methods which would come into their own in the conquest of the New World. There were marked similarities between the methods of the Reconquista and those adopted for the conquest of the Canaries, which itself was regarded by Ferdinand and Isabella as part of Castile’s holy war against the infidel. The occupation of the Canaries, like the Reconquista, was a blend of private and public enterprise. Much of the Reconquista, especially in its later stages, had been conducted under the control of the Crown. The State also participated in the Canary expeditions, which were partly financed by the Crown and public institutions. But private enterprise operated alongside the State. Fernández de Lugo made a private contract with a company of Sevillian merchants – one of the first contracts of the type later used to finance the expeditions of discovery in America. Even an expedition entirely organized and financed under private auspices, however, was still dependent on the Crown for its legal authority. Here again the Reconquista provided a useful precedent. It had been the practice for the Crown to make contracts with leaders of military expeditions against the Moors. It seems probable that these contracts inspired the document known as the capitulación, which later became the customary form of agreement between the Spanish Crown and the conquistadores of America.
The purpose of capitulaciones was to reserve certain rights to the Crown in newly conquered territories, while also guaranteeing to the leader of the expedition due mercedes or rewards for his services. These rewards might consist of an official position such as the post of adelantado of Las Palmas conferred upon Fernández de Lugo – adelantado being a hereditary title granted by medieval Castilian kings and conferring upon its holder special military powers and the rights of government over a frontier province. The leader of an expedition would also expect to enjoy the spoils of conquest, in the shape of movable property and captives, and to receive grants of land and a title of nobility, like his predecessors during the Reconquista. In making capitulaciones of this type, the Crown was clearly bargaining away many of its rights, but generally it had no alternative. When it provided financial assistance, as it did for Columbus and Magellan, it could hope to make rather more favourable conditions, but the work of conquest and colonization had to be left largely to private enterprise.