Why do Portuguese and Spanish historians sometimes give different emphasis to Ferdinand Magellan’s accomplishments?

The differing emphasis placed on Ferdinand Magellan by Portuguese and Spanish historians stems from his shift in national allegiance during the 16th century, a period preceding modern nationalism when explorers often pledged loyalty to whichever monarch sponsored their ambitions.1

• Portuguese Perspective: Because Magellan entered the service of the Spanish crown after failing to secure support in his homeland, Portuguese historians have historically been reluctant to grant him the same level of recognition afforded to other prominent Portuguese navigators, such as Vasco da Gama and Bartolomeu Dias.1
• Spanish Perspective: Conversely, Spanish historians have frequently shifted the focus of the expedition's success toward Juan Sebastián del Cano, the Basque navigator who completed the first circumnavigation of the globe after Magellan’s death in the Philippines.12

Despite these historiographical biases, Magellan remains recognized for his critical role in discovering the Strait of Magellan and demonstrating the vast scale of the Pacific Ocean, ultimately providing practical proof of a spherical Earth.1