Treasure Fleet (Civ5)/Civilopedia

Once the Spanish arrived in the Americas and begun shipping their new finds and treasures back to Europe, they needed to develop a new, more efficient method of sailing in order to combat the increased pressure of pirate raids on their ships. The Spanish Treasure Fleet was the answer - a special convoy system of ships which was strictly regulated in both docking and sailing practices. Ships departing from the Americas along the Spanish Main were instructed to sail en masse along a specific sea lane, allowing them to be more easily protected by a smaller armed force. These ships then only sailed to restricted, protected, port towns (like Seville), again lessening the risk of pirate raid.
The Treasure Fleet was employed by Spain from the 16th to 18th century with much success, and is still counted as one of the most profitable and effective naval operations in history. However, the loss of some important coastal cities along the Spanish Main in the 1700s began to threaten the continued existence of the fleet. In a bid to combat this, King Charles III loosened the rigorous system in 1765, and gave more colonies access to the fleet in the 1780s. However, the last full fleet sailed in 1790 and shipping between the two continents was relegated to smaller groups of ships on an as-needed basis.