In 1402, the Castilian colonisation of the islands began with the expedition of the French explorers Jean de Béthencourt and Gadifer de la Salle, nobles and vassals of Henry III of Castile, to Lanzarote. From there, they went on to conquer Fuerteventura (1405) and El Hierro. These invasions were ‘brutal cultural and military clashes between the indigenous population and the Castilians’ lasting over a century due to formidable resistance by indigenous Canarians. Professor Mohamed Adhikari has defined the conquest of the islands as a genocide of the Guanches.

Béthencourt received the title King of the Canary Islands, but still recognised King Henry III as his overlord. It was not a simple military enterprise, given the aboriginal resistance on some islands. Neither was it politically, since the particular interests of the nobility (determined to strengthen their economic and political power through the acquisition of the islands) conflicted with those of the states, particularly Castile, which were in the midst of territorial expansion and in a process of strengthening of the Crown against the nobility.

Historians distinguish two periods in the conquest of the Canary Islands:

Aristocratic conquest (Conquista señorial). This refers to the early conquests carried out by the nobility, for their own benefit and without the direct participation of the Crown of Castile, which merely granted rights of conquest in exchange for pacts of vassalage between the noble conqueror and the Crown. One can identify within this period an early phase known as the Betancurian or Norman Conquest, carried out by Jean de Bethencourt (who was originally from Normandy) and Gadifer de la Salle between 1402 and 1405, which involved the islands of Lanzarote, El Hierro and Fuerteventura. The subsequent phase is known as the Castilian Conquest, carried out by Castilian nobles who acquired, through purchases, assignments and marriages, the previously conquered islands and also incorporated the island of La Gomera around 1450.

Royal conquest (Conquista realenga). This defines the conquest between 1478 and 1496, carried out directly by the Crown of Castile, during the reign of the Catholic Monarchs, who armed and partly financed the conquest of those islands which were still unconquered: Gran Canaria, La Palma and Tenerife. This phase of the conquest came to an end in the year 1496, with the dominion of the island of Tenerife, bringing the entire Canarian Archipelago under the control of the Crown of Castile.

Béthencourt also established a base on the island of La Gomera, but it would be many years before the island was fully conquered. The natives of La Gomera, and of Gran Canaria, Tenerife, and La Palma, resisted the Castilian invaders for almost a century. In 1448 Maciot de Béthencourt sold the lordship of Lanzarote to Portugal’s Prince Henry the Navigator, an action that was accepted by neither the natives nor the Castilians. Despite Pope Nicholas V ruling that the Canary Islands were under Portuguese control, the crisis swelled to a revolt which lasted until 1459 with the final expulsion of the Portuguese. In 1479, Portugal and Castile signed the Treaty of Alcáçovas, which settled disputes between Castile and Portugal over the control of the Atlantic. This treaty recognized Castilian control of the Canary Islands but also confirmed Portuguese possession of the Azores, Madeira, and the Cape Verde islands, and gave the Portuguese rights to any further islands or lands in the Atlantic that might be discovered.

The Castilians continued to dominate the islands, but due to the topography and the resistance of the native Guanches, they did not achieve complete control until 1496, when Tenerife and La Palma were finally subdued by Alonso Fernández de Lugo. As a result of this ‘the native pre-Hispanic population declined quickly due to war, epidemics, and slavery’. The Canaries were incorporated into the Kingdom of Castile.