The result of long-standing commercial tensions, the war was primarily fought in the Caribbean; the British tried to capture key Spanish ports in the region, including Porto Bello and Chagres in Panama, Havana, and Cartagena de Indias in present-day Colombia.

After a series of unsuccessful assaults in the campaign, the British were forced to retreat, having suffered over 9,500–11,500 fatalities, in great part to disease, and considerable material losses.

[27] As the French previously discovered, high costs meant the majority of the profits which could be gained from the concessions were in smuggling contraband goods, which evaded import duties and deprived the Spanish colonial authorities of much needed revenue.

In the Anglo-Spanish War of 1727 to 1729, Spain laid siege to Gibraltar, while Britain blockaded Portobello; both attempts failed and the two countries made peace in the Treaty of Seville but the underlying issues for the conflict remained unresolved.

Pressure from the British public for a declaration of war arose out of a combination of a political campaign to remove Robert Walpole, the long-serving Prime Minister, and a desire for greater commercial access in Spanish America.

[34] The first goal of the expedition was to capture Havana, the most important of the Spanish ports because it had facilities where ships could be refitted and, by 1740, it had become Spain's largest and most active shipyard.

Vernon, despite his earlier failed raid on Cartagena, was not convinced that a large-scale attack on a heavily fortified city would prove to be as successful as his smaller Portobello assault had been.

The British would have bases from which to launch attacks into the interior, and Spain would have limited access to deep water ports on the eastern coast of their American colonies and therefore be unable to resupply their inland forces.

A quick capture of Havana and its dry dock was imperative and it was the favored objective of Newcastle and Sir Charles Wager, First Lord of the Admiralty,[48] but Britain's divided ministry left the course of the campaign up to Vernon and others at a council of war held in Jamaica.

Its harbour, considered by some observers to be one of the finest in the world, served the galleons of the commercial fleet (Galeones a Tierra Firme y Perú) that annually assembled at Havana to convoy the immense revenues of gold and silver from New Granada and Peru to Spain.

[50] The shallow coastal shelf extending out from the city walls prevented a direct attack from the sea, while a high water table hindered sapping and exposed unacclimatised troops to disease.

[51] After Cartagena's capture in 1585 by an English force under Sir Francis Drake, its fortifications were rebuilt by the Italian engineer Battista Antonelli.

Initially, contrary winds delayed the sailing until most of the shipboard provisions were consumed and a steep increase of sickness[65] occurred among the ships' crews.

It ran between two narrow peninsulas and was defended on one side by the fort of San Luis, Boca Chica Castle, with four bastions having some 49 cannon, three mortars and a garrison of 300 soldiers under the command of the chief engineer, Carlos Desnaux.

[74] Before settling to disembark, Vernon silenced the batteries of the fortresses of Chamba, San Felipe and Santiago defended by Lorenzo Alderete from Malaga.

After attacking the fort of Punta Abanicos in the Barú Peninsula, defended by Jose Polanco Campuzano from Santo Domingo[75][76] and a week of bombardment, the British planned to land near the smaller access channel, Boca Chica, with 300 grenadiers.

The operation against Boca Chica cost the British army 120 killed and wounded, additionally 250 died from the diseases of yellow fever and malaria, and 600 sick were hospitalized.

With the capture of San Luis and other outlying defensive works, the fleet passed through the Boca Chica channel into the lagoon that made up the harbor of Cartagena.

But the attack started late and the initial advance on Lazaro was made near dawn, at 4:00 am 20 April, by a forlorn hope of 50 picked men followed by 450 grenadiers commanded by Colonel Wynyard.

Wynyard was led to a steep approach and, as the grenadiers scrambled up the slope, they were received with a deadly volley of musket fire at thirty yards/metres from the Spanish in the entrenchments.

[90][91] Don Blas de Lezo's plan had been that, given the overwhelming force against him, he would attempt to conduct a fighting withdrawal and delay the British long enough until the start of the rainy season at the end of April.

[23] The Spanish also suffered severely from disease including Blas de Lezo himself, who died a few weeks after falling ill from the plague from unburied bodies.

[95] Of the 3,600 American colonists, who had volunteered, lured by promises of land[96] and mountains of gold,[97] most died of yellow fever, dysentery, and outright starvation.

[99]The main reasons for the British defeat were the failure of the British to find united leadership after the commander in chief, General Charles Cathcart, died of dysentery en route; the logistic inability to land siege artillery and ammunition near to Cartagena; the impediments made by Vernon that prevented involvement of his line ships to support the infantry forces; and the effective Spanish maneuvers carried out by the viceroy Sebastián de Eslava, Admiral Blas de Lezo and Colonel Carlos Suivillars.

[100] There is no evidence for the claim made in recent years by works published in Spain that Admiral Vernon sent a letter to Blas de Lezo saying that "We have decided to retreat, but we will return to Cartagena after we take reinforcements in Jamaica", to which Blas de Lezo supposedly responded: "In order to come to Cartagena, the English King must build a better and larger fleet, because yours now is only suitable to transport coal from Ireland to London".

The staggering losses suffered by the British compromised all the subsequent actions by Vernon and Wentworth in the Caribbean and most ended in acrimonious failure[104] despite reinforcements of 1,000 troops from Jamaica and 3,000 regular infantry from Britain.

[105] Vernon and Wentworth were both recalled to Britain in September 1742, with Chaloner Ogle taking command of a very sickly fleet that had less than half its sailors fit for duty.

The weakened British forces led by Charles Knowles made raids upon the Venezuelan coast, attacking La Guaira in February 1743 and Puerto Cabello in April, though neither operation was particularly successful.

[108] It was not until Commodore Richard Lestock, commander of one of Vernon's divisions at Cartagena, returned to Europe with ships from the Caribbean fleet, that Britain reinforced its presence in the Mediterranean.

[110] In 2014, whilst on his royal visit to Colombia, Prince Charles in cooperation with the city authorities unveiled a plaque which commemorated the British casualties of the battle.