How did Charles II of Spain’s death lead to the War of the Spanish Succession?

The death of the childless Charles II in 1700 triggered the War of the Spanish Succession because it left the vast Spanish Empire without a clear, undisputed heir, threatening the European balance of power.1

Both the House of Bourbon (France) and the House of Habsburg (the Holy Roman Empire under Leopold I) held dynastic claims to the throne. While European powers initially sought to avoid conflict through partition treaties, Charles II adamantly opposed dividing his inheritance. In his final will, he named Philip, duc d’Anjou—a grandson of Louis XIV—as his sole heir.213

When Louis XIV accepted the will and recognized Philip as King of Spain, he provoked the Maritime Powers (England and the United Provinces), who feared the expansion of French power and the loss of trade access. The subsequent conflict became a struggle to prevent the unification of the French and Spanish crowns or the restoration of a massive Habsburg empire, ultimately reshaping the geopolitical landscape of Europe.213