The Blockade of Porto Bello was a failed British naval action against the Spanish port of Porto Bello in present-day Panama between 1726 and 1727 as part of the Anglo-Spanish War. The British were attempting to blockade the port to stop the Spanish treasure fleet leaving for Spain with its valuable cargo. However tropical disease took its toll of the seamen to the extent that the British had to leave to re-crew, during which time the Spanish were able to re-commence shipping operations.
Background
Spain and Britain had come into conflict during the 1720s over a number of issues, and had recently been at war with each other during the War of the Quadruple Alliance. Disputes over trade were a major cause of aggravation to Anglo-Spanish relations, combined with a fear in Britain that Spain had made an alliance with Austria as the precursor to declaring war on Britain and its ally France. The British decided to try to weaken Spain and discourage them from pursuing the Austrian alliance by denying the Spanish the treasure fleets on which metropolitan Spain had become dependent.
In March 1726 an expedition was sent to the Spanish West Indies, under Rear-Admiral Francis Hosier, for the purpose of blocking up the Spanish galleons or seizing them should they venture out. The former privateer and governor of the Bahamas Woodes Rogers, who was in London at the time, was consulted by the Government as to the probable means and route the Spaniards would adopt to get their treasure home. From past experience Rogers probably knew more than any other person then in England of the difficulties of the voyage, and in conjunction with Capt. Jonathan Denniss, he delivered a report dated 10 November 1726 to Viscount Townshend, Secretary of State, to prepare Hosier for his task:
"My Lord, According to what your lordship was pleased to command us, we have considered the account given by Mr Cayley from Cadiz to his grace the Duke of Newcastle of three men-of-war and a ship of ten guns being sent under the command of Admiral Castanetta from that port in the month of May last, with canon and land forces which, your lordship apprehends, may be ordered round Cape Horn, in order to bring to Spain the bullion now detained at Panama, and we give it your lordship as our opinion, that it is not only improbable, but almost impracticable, for the following reasons: First because of the time of year in which those ships sailed from Cadiz, which is at least three months to soon to attempt getting round Cape Horn, or through the Straits of Magellan, especially if the nature of the ships be considered, and their being deeply laden, and having canon and land forces on board. Secondly, because there can be no need of canon in Peru or Chile, those provinces abounding in metal for casting them, and the Spaniards being able to do it (as they always have done) cheaper and full as well as in Spain, and as to the soldiers, the transporting them that way seems altogether improbable because of the many better methods there are of doing it. Thirdly, my Lord, as the bullion is now at or near Panama, the embarking it thence to Lima, and so to be brought round Cape Horn, will require so prodigious an expense both of time and money, that renders the doing of it extremely improbable. 'Tis true, my Lord, were the money now at Potosi or Lima 'twould be easy enough to bring it round Cape Horn, or rather overland to Buenos Aires, where Castanetta might be gone to receive it, but as it is not, the bringing of it from Panama to Lima will require too long a time, because of the difficulty of the navigation from the former to the latter place, being against both winds and currents, so that the Spanish ships are commonly from six to eight or ten months performing the voyage, and though the French formerly often came with their money round the Cape to France, yet your Lordship will consider their tract of trade was never to leeward, or to the northward of the coasts of Peru, by which means the greatest fatigue of the voyage was avoided.