The matter was the more important because the male heir to the throne was so feeble that it was evident that the Austrian line of Spanish kings would end in him.

The desire to put a French prince on the Spanish throne--either himself, thus uniting the two crowns, or else one of his family, thus putting the House of Bourbon in authority on both sides of the Pyrenees--was the false light which led Louis astray during the rest of his reign, to the final destruction of the sea power of France and the impoverishment and misery of his people.
Louis failed to understand that he had to reckon with all Europe.

The direct project on the Spanish throne had to wait for a vacancy; but he got ready at once to move upon the Spanish possessions to the east of France.
In order to do this more effectually, he cut off from Spain every possible ally by skilful diplomatic intrigues, the study of which would give a useful illustration of strategy in the realm of politics, but he made two serious mistakes to the injury of the sea power of France.

Portugal had until twenty years before been united to the crown of Spain, and the claim to it had not been surrendered.

Louis considered that were Spain to regain that kingdom she would be too strong for him easily to carry out his aims.