Book starting points for Spanish treasure fleets

What books explain the Spanish convoy system and how it survived for centuries?

Begin with Timothy Walton on the Spanish treasure fleets, then use Strategy Before Clausewitz and comparative Portuguese history for wider context.

Timothy Walton's study of the Spanish treasure fleets is recommended as an English-language starting point. Strategy Before Clausewitz gives a broader account of strategy between 1400 and 1830. Additional specialist material exists in Spanish, making the English-language route narrower than the full literature. A short history of Portugal is offered as a useful comparative entry into another maritime empire and its colonial system.