Background:

As part of the Treaty of Utrecht which ended the War of the Spanish Succession, Britain received a thirty-year trade agreement (an asiento) from Spain which permitted British merchants to trade up to 500 tons of goods per year in the Spanish colonies as well as sell an unlimited number of enslaved people. This asiento also provided inroads in Spanish America for British smugglers. Though the asiento was in effect, its operation was often hindered by military conflicts between the two nations which occurred in 1718-1720, 1726, and 1727-1729. In the wake of the Anglo-Spanish War (1727-1729), Britain granted Spain the right to stop British ships to ensure that the terms of the agreement were being respected. This right was included in the Treaty of Seville which ended the conflict.

Believing that the British were taking advantage of the agreement and smuggling, Spanish authorities began boarding and seizing British ships, as well as holding and torturing their crews. This led to an increase in tensions and an up swell of anti-Spanish sentiment in Britain. Though issues were mitigated somewhat in the mid-1730s when British First Minister Sir Robert Walpole supported the Spanish position during the War of the Polish Succession, they continued to exist as the root causes had not been addressed. Though wishing to avoid war, Walpole was pressured into sending additional troops to the West Indies and dispatching Vice Admiral Nicholas Haddock to Gibraltar with a fleet. In return, King Philip V suspended the asiento and confiscated British ships in Spanish ports.

Wishing to avoid a military conflict, both sides met at Pardo to seek a diplomatic resolution as Spain lacked the military resources to defend its colonies while Britain did not wish interfere with profits from the slave trade. The resulting Convention of Pardo, which was signed in early 1739, called for Britain to receive £95,000 in compensation for damages to its shipping while paying £68,000 in back revenue to Spain from the asiento. Additionally, Spain agree to territorial limits in regard to searching British merchant vessels. When the terms of the convention were released, they proved unpopular in Britain and the public clamored for war. By October, both sides had repeatedly violated the convention's terms. Though reluctant, Walpole officially declared war on October 23, 1739. The term "War of Jenkins' Ear" derives from Captain Robert Jenkins who had his ear cut off by the Spanish Coast Guard in 1731. Asked to appear in Parliament to recount his tale, he reputedly displayed his ear during his testimony.

Porto Bello

In one of the first actions of the war, Vice Admiral Edward Vernon descended on Porto Bello, Panama with six ships of the line. Attacking the poorly defended Spanish town, he quickly captured it and remained there for three weeks. While there, Vernon's men destroyed the city's fortifications, warehouses, and port facilities. The victory led to the naming of Portobello Road in London and public debut of the song Rule, Britannia! With the beginning of 1740, both sides anticipated that France would enter the war on the side of Spain. This led to invasion scares in Britain and resulted in the bulk of their military and naval strength being retained in Europe.

Florida

Overseas, Governor James Oglethorpe of Georgia mounted an expedition into Spanish Florida with the goal of capturing St. Augustine. Marching south with around 3,000 men, he arrived in June and commenced constructing batteries on Anastasia Island. On June 24, Oglethorpe began a bombardment of the city while ships from the Royal Navy blockaded the port. In the source of the siege, British forces suffered a defeat at Fort Mose. Their situation worsened when the Spanish were able to penetrate the naval blockade to reinforce and resupply St. Augustine's garrison. This action forced Oglethorpe to abandon the siege and withdraw back to Georgia.

Anson's Cruise

Though the Royal Navy was focusing on home defense, a squadron was formed in late 1740, under Commodore George Anson to raid Spanish possessions in the Pacific. Departing on September 18, 1740, Anson's squadron encountered severe weather and was plagued by disease. Reduced to his flagship, HMS Centurion (60 guns), Anson reached Macau where he was able to refit and rest his crew. Cruising off the Philippines, he encountered the treasure galleon Nuestra Señora de Covadonga on June 20, 1743. Overhauling the Spanish vessel, Centurion captured it after a brief fight. Completing a circumnavigation of the globe, Anson returned home a hero.

Cartagena

Encouraged by Vernon's success against Porto Bello in 1739, efforts were made in 1741 to mount a larger expedition in Caribbean. Assembling a force of over 180 ships and 30,000 men, Vernon planed to attack Cartagena. Arriving in early March 1741, Vernon's efforts to take the city were plagued by a lack of supplies, personal rivalries, and rampaging disease. Endeavoring to defeat the Spanish, Vernon was forced to withdraw after sixty-seven days which saw around a third of his force lost to enemy fire and disease. News of the defeat ultimately led to Walpole leaving office and being replaced by Lord Wilmington. More interested in pursuing campaigns in the Mediterranean, Wilmington began to wind down operations in the Americas.

Repulsed at Cartagena, Vernon attempted to take Santiago de Cuba and landed his ground forces at Guantánamo Bay. Advancing against their objective, the British were soon bogged down by disease and fatigue. Though the British attempted to continue the invasion, they were forced to abandon the operation when they met heavier than anticipated opposition. In the Mediterranean, Vice Admiral Haddock worked to blockade the Spanish coast and though he took several valuable prizes, was unable to bring the Spanish fleet to action. British pride at sea was also marred by the damage inflicted by Spanish privateers which attacked unescorted merchantmen around the Atlantic.

Georgia

In Georgia, Oglethorpe remained in command of the colony's military forces despite his earlier failure at St. Augustine. In the summer of 1742, Governor Manuel de Montiano of Florida advanced north and landed on St. Simons Island. Moving to meet this threat, Oglethorpe's forces won the Battles of Bloody Marsh and Gully Hole Creek which compelled Montiano to retreat back to Florida.

Absorption into the War of the Austrian Succession

While Britain and Spain were engaged in the War of Jenkins' Ear, the War of the Austrian Succession had broken out in Europe. Soon drawn into the larger conflict, the war between Britain and Spain was subsumed by mid-1742. While the bulk of the fighting occurred in Europe, the French fortress at Louisbourg, Nova Scotia was captured by New England colonists in 1745.

The War of the Austrian Succession came to an end in 1748 with the Treaty of Aix-la-Chapelle. While the settlement dealt with the issues of the wider conflict, it did little to specifically address the causes of the 1739 war. Meeting two years later, the British and Spanish concluded the Treaty of Madrid. In this document, Spain bought back the asiento for £100,000 while agreeing to allow Britain to trade freely in its colonies.