How did Maximilian I’s marriage alliances connect the Habsburgs to Spain?

Maximilian I expanded the influence of the House of Habsburg through a strategic policy of marriage alliances, famously summarized by the phrase Bella gerant alii, tu felix Austria nube ("Let others wage wars: you, fortunate Austria, marry").1

His primary connection to Spain was established through the marriage of his son, Philip I, to Joan, the daughter of Ferdinand II and Isabella I. As Joan was the prospective heiress to the kingdoms of Castile and Aragon, this union secured the Spanish succession for the Habsburg family. Additionally, Maximilian arranged for his daughter, Margaret of Austria, to marry the Spanish crown prince in 1497, further cementing these ties.123

These matrimonial achievements ensured that Maximilian’s grandson, Charles V, inherited both the Burgundian and Spanish dominions, including the Spanish colonies in America, effectively establishing the Habsburg dynasty in Spain for nearly two centuries.12