The Spanish treasure fleets (or West Indies Fleet from Spanish Flota de Indias) was a convoy system adopted by the Spanish Empire from 1566 to 1790. The convoys were general purpose fleets used for transporting a wide variety of items, including agricultural goods and sometimes even lumber, manufactures and various metal resources and luxuries, most famously silver and gold, but also gems, pearls, spices, sugar, tobacco, silk, and other exotic goods from the Spanish colonies to Spain. Manufactures such as tools and other everyday items as well as Spanish emmigrants were transported in the opposite direction.

History

thumb|Pedro Menéndez de Avilés, designer of the treasure fleets system
Spanish ships had brought treasure from the New World since Christopher Columbus's first expedition of 1492. The government started a system of convoys in the 1560s in response to attacks by French privateers. The main procedures were established after the recommendations of Pedro Menéndez de Avilés, an experienced admiral and personal adviser of king Phillip II. The treasure fleets sailed along two sea lanes. The main one was the Spanish Caribbean fleet or Flota de Indias, which departed in two convoys from Seville, bound for ports like Veracruz, Portobelo and Cartagena before making a rendevous at Havana in order to return together to Spain. A secondary route was that of the Manila Galleons or Galeón de Manila which linked the Philippines to Acapulco in Mexico. From Acapulco, the Asian goods were transhipped to Veracruz to be loaded on to the Caribbean treasure fleet for shipment to Spain.

Spain strictly controlled the trade through the Casa de Contratación based in Seville. By law, the colonies could trade only with the one designated port in the mother country. Maritime archaeology has shown that the quantity of goods transported was usually much higher than that recorded at the Archivo General de Indias. Spanish merchants and Spaniards acting as fronts (cargadores) for foreign merchants resorted to contraband to transport their cargoes untaxed. The Crown of Spain taxed the wares and precious metals of private merchants at a rate of 20%, a tax known as the quinto real (royal fifth).
This monopsony lasted for over two centuries, in which Spain became the richest country in Europe. The Habsburgs used the wealth to fight wars in the 16th and 17th centuries against the Ottoman Empire and with most of the major European powers. Due to inflation in the 17th century, the flow of precious metals from the Indies gradually damaged and depressed the Spanish economy. Spain also lost any financial support from Europeans bankers by 1690.

The exports' economic importance also declined with the drop of production of the American precious metals mines, such as Potosí. Numbering just 17 ships in 1550, the fleets expanded to more than 50 much larger vessels by the end of the century. By the second half of the 17th century, that number had dwindled less than half of its peak, with many of its remaining ships old and in poor repair. As economic conditions gradually recovered from the last decades of the 17th century, the fleet operations slowly expanded again, once again becoming prominent during the reign of the Bourbons in the 18th century.

The Spanish trade of goods and precious metals was threatened until the mid-18th century by Spain's colonial rivals who seized small bases along the Spanish Main and the Spanish West Indies. The English acquired small islands like St Kitts in 1624 and seized Jamaica in 1655, the French Saint-Domingue in 1625 and the Dutch Curaçao in 1634. In 1739, Admiral Edward Vernon raided Porto Bello, but in 1741 his massive campaign against Cartagena de Indias ended in disaster. In 1762, the British briefly occupied Havana and Manila, forcing temporary changes to the usual pattern of Spanish fleet operations, using a greater number of smaller fleets visiting a greater variety of ports.
Only a couple of years later (1764) Havana and Manila were restored to Spain, and operations in the Atlantic and Pacific continued as usual.
Charles III began loosening the system in 1765. In the 1780s Spain opened its colonies to free trade. In 1790, the Casa de Contratación was abolished. The last regular treasure fleet sailed that year. Thereafter small groups of naval frigates were assigned to the transfer of bullion as required.
Despite the general perception that many Spanish galleons were captured by English or Dutch privateers, few fleets were actually lost to enemies in the course of the flota's long career. Only Piet Hein managed to capture the fleet in 1628 and bring the whole cargo safely to the Dutch Republic. In 1656 and 1657 Robert Blake destroyed the fleet, but the Spaniards saved most of the silver on board and the English admiral only managed to capture a galleon. The 1702 treasure fleet was destroyed in the Battle of Vigo Bay when surprised at port, but the Spanish sailors had already unloaded most of its cargo. None of these attacks took place in open seas. In the case of the Manila galleons, only four were ever captured by British warships: The Santa Anna by Thomas Cavendish in 1589, the Encarnación in 1710, the Covadonga by George Anson in 1743 and the Santísima Trinidad in 1762. Two other British attempts were foiled by the Rosario in 1704 and the Begonia in 1710. These losses and those due to hurricanes were heavy economic blows when they occurred. The treasure fleets, however, must be counted as among the most successful naval operations in history. Moreover, from a commercial point of view, some key components of today's world economic system were made possible by the success of the Spanish treasure fleets.
Wrecks of Spanish treasure ships, whether sunk in naval combat or by storms (those of 1622, 1715 (1715 Treasure Fleet) and 1733 being among the worst), are a prime target for modern treasure hunters. Many, such as the Nuestra Señora de Atocha, have been salvaged.