Why did Leopold I oppose Philippe, duc d’Anjou, becoming king of Spain?

Leopold I opposed the accession of Philippe, duc d’Anjou, to the Spanish throne primarily because he viewed the Spanish succession as a central aim of his politics and believed the Spanish heritage should be defended by force of arms to maintain the unity of the House of Habsburg.1

Leopold’s opposition was driven by several key factors:

• Dynastic Claims: Leopold sought the Spanish throne for his own family, specifically his younger son, the archduke Charles (later Charles VI). He believed the two lines of the Habsburgs should be considered parts of the same entail.21
• Balance of Power: Leopold, along with the Maritime Powers (England and the United Provinces of the Netherlands), feared the significant aggrandizement of French power under the House of Bourbon. The prospect of a Bourbon prince ruling Spain threatened to disrupt the European balance of power.234
• Economic Concerns: The Maritime Powers were particularly concerned that a Bourbon-controlled Spain would lead to the loss of their established trade with Spain and the West Indies.2

When Charles II died in 1700 and named Philippe as his sole heir, Leopold refused to accept the will, leading to the War of the Spanish Succession.214