As early as 1739 the ministry had decided they would make at least one big play in the Caribbean. The plan called for a joint operation between an army of 12,000 British and American colonial soldiers backed by the largest naval squadron-29 capital ships and almost a hundred smaller war and support vessels-ever assembled in the Americas. This was an unprecedented projection of power across 4,000 miles of open ocean. Owing to Vernon’s actions the target was essentially preordained: Cartagena de Indias. The city’s defenses had been built up quite a bit since Francis Drake’s little pirate romp, but Vernon was confident he could crack it. Reassuring the Admiralty he wrote “I coasted their shore…and I think I now know as much of the avenues to their harbor as they do themselves”. To Vernon, this was to be his crowded hour, and a real chance to cement his legacy with the most smashing victory of a generation.
Given the boulder sized rock in their fist, it was easy to see why Vernon and the British were confident. Cartagena de Indias had a garrison of between 3-6,000 men from mainland Spain and the colonies, and about 600 indigenous troops serving in some capacity; and that was after a recent flotilla of Spanish reinforcements following the attack on Porto Bello. To meet the naval threat Admiral Eslava had just six ships of the line stationed in the city. To compound matters, the larger Spanish West Indies squadron was even weaker than it had been when the war began. It never pays to tempt fate on a boat, and the Spanish ship of the line Invincible paid for the hubris of its namesake when a bolt of lightning struck the ship at anchor in Havana. The resulting fire reached the powder magazine, setting off an explosion that took out the vessel, some of the surrounding ships, and set a good chunk of Havana ablaze. Rubbing salt in the wounds a large French squadron under the Marquis d’Antin had been sent to the region in 1740. France was not at war with Britain, but d’Antin was there to remind the British that there would be larger consequences if they were not careful. Which meant it was horrible timing that d’Antin had sailed off for “Old France” right as the British reinforcements arrived.
But the Spanish had a few advantages of their own. For one thing they knew the British were on their way. It was impossible not to, given Vernon had all but yodeled his plans to them with the reconnaissance missions. Best of all were the Spanish commanders, Eslava and Don Blas de Lezo y Olavarrieta. Lezo was a Basque admiral, and something of a legend by the time of his posting. He was nicknamed “Halfman” by his soldiers, as he had lost a leg, an arm, and an eye in a lifetime of service in Spain’s army. The two leaders and their chief engineer feuded somewhat, but ultimately coordinated on how to best defend Cartagena from the coming storm.
The other benefit was that Cartagena de Indias was probably the most fortified spot in the region. Multiple assaults by the British and the French had caused Spain to add layer upon layer to defenses. At the center was San Lazaro, a citadel looming over the city from a nearby hill. The fortress was itself a series of interconnected walls, each with overlapping lines of sight to ensure an attacker would always be in a crossfire on approach. Like some murderous anthill the citadel was also honeycombed with tunnels, and Lezo had made the position even stronger with a series of trenches dug around the base of the hill. But even getting to San Lazaro would be a trial. In the past Cartagena had two harbors, Boca Grande and Boca Chica. As the names imply, one was wide and the other fairly narrow and reserved for deep draft ships. In the time since Drake’s little romp Boca Grande had been rendered unusable by several shipwrecks and an enlarged sandbar, and the only entry to the outer harbor was now the slimmer Boca Chica. Understandably the downsizing favored the defenders. Lezo parked four of his ships at the entrance, complementing harbor booms and four small battery forts to make the approach treacherous. Perhaps the biggest advantage of all was just that the Spanish could just sit tight and wait, the British would have to figure out how they were actually getting to Panama.
Given the scale of the operation, the logistics involved posed an amazing challenge in the age of sail. Which is another way of saying everything went wrong from the start. With their eyes on the European chessboard, the British government only dispatched two veteran regiments, along with 6,000 newly recruited marines. While the colonies were eager to supply 4,000 of their own volunteers, it was also going to take some time to hammer even rudimentary training into the new recruits. Added to that challenge, ferrying men from Massachusetts, Rhode Island, Pennsylvania, Virginia etc. to Jamaica took time as well. From the moment they set foot in the region, the colonial forces got a taste of the microbial and viral cornucopia awaiting them on the campaign and sickness began to wreak havoc on the brave volunteers of Gooch’s American Regiment.
Then there was the bigger problem of getting more ships and men from Britain, which took even longer. To make matters worse, the voyage across the Atlantic was a bad trip for everyone involved. The commander of the ground forces, Lord Charles Cathcart, along with another 483 men died on the miserable journey. Cathcart’s replacement was the less experienced Brigadier General Thomas Wentworth, who Vernon immediately decided was his inferior. When the combined force was finally assembled on January 9, 1741 sans Cathcart, the clock was already ticking until hurricane season hit the region.
While Lezo and Eslava had known an attack was coming, they were still flabbergasted by the size of it when Vernon’s fleet arrived on March 15th. The Spanish fleet had compounded the defender’s challenges by resupplying at Cartagena just before the British pulled into view. When the fleet had moseyed off to inspire the rage of Zeus they left with several months’ worth of food and water, which meant the defenders would struggle to endure a prolonged siege. Nevertheless, Lezo and his men prepared to meet the British.
 Marks, K. M. (1999). “Like thunder and lightning:” British force projection in the West Indies, 1739-1800 (Doctoral dissertation, Ohio State University).
 There’s a lot of ambiguous terminology in the secondary sourcing. It’s not clear to the author if these men were paid auxiliary “archers”, “slave labor”, or just forcibly conscripted from the region for the defense.
 Reminder: traversing an ocean in a wooden boat is a horrible time.
 Funny story about dates here. By 1741 Spain switched to the Gregorian Calendar, but Britain was still using the Julian one, as such the author is erring on the side of the former. The difference is about ten days or so, which makes hell of the timeline of specific events.