Well-guarded or no, all of the Spanish positions around Boca Chica were in range of the Royal Navy’s heavy guns. One by one the Spanish forts and ships were hammered by artillery. Three of the four were hammered into submission, leaving only the larger Fort San Luis guarding the mouth of Boca Chica. Wentworth’s troops landed and, per the playbook of European siege warfare, began deploying to besiege San Luis. As this was a combined operation, both the army and the navy had to recognize when to lead and when to support one another. At San Luis, Vernon proved he was absolutely the worst kind of backseat driver. Needling dispatches urging Wentworth to attack immediately poured in over the next few days, filled with platitudes like “the Enemy will not stand the native Courage of our Men when we can come to hands with them”. It was enough to drive anyone to distraction. Admittedly the general was probably a better second fiddle anyways, but only to another officer of the British Army. Since Cathcart had pooped himself to death somewhere in the Atlantic this simply meant Wentworth moved slower and more cautiously than Vernon liked, while Vernon in turn mouthed off about a land war he knew little about.
Nor had either man planned on the ferocious resistance and discipline of the Spanish. Instead of sweeping aside the defense at Boca Chica in a few days, it had taken more than two weeks just to reduce the defenses. It took until April for a sustained bombardment and assault on the fort to start showing real progress. Where the British were divided and fractious, nothing could shake the Spanish focus. This included actual artillery. While holding a council of war aboard the flagship Galicia a cannon round blasted into Admiral Lezo’s cabin and literally blew apart the stool Eslava was sitting on, showering both men in splinters. Since Lezo had been aggressively disarmed once, a near miss and porcupining was no big deal. New chairs were brought in and the men continued to plan the next phase of the defense.
As San Luis could no longer hold out, Eslava and Lezo quietly evacuated the fortress in small groups. To slow the British up further, most of the Spanish fleet was scuttled in the mouth of Boca Chica to block the entrance. By April 5th the British had captured San Luis from the skeleton defense left behind, but it took another two agonizing weeks for the British to clear the Spanish warships and clean out the remaining defenses. Even so, the way to the city was open. Vernon was jubilant, and he sent a messenger racing back to London with the good news. The premature report had the British drunk on patriotism all over again. Church bells rang, songs were written, and commemorative medals were rushed out the door to cash in on Vernon’s triumph.
But the situation in Cartagena had not quite lived up to expectations. The month in Panama was beginning to take its toll on the invaders. The climate was bad, and the diseases worse. Before San Luis was captured maybe 1,500 of Wentworth’s 8,000 soldiers were out of commission from gunfire or yellow fever. As the month wore on Wentworth reported that “the excessive Heat not only retarded the Work, but proved fatal to most of the Europeans”. The losses were particularly horrific among the North American troops, who had not realized signing up to fight for Queen and Country meant dying in terrible agony somewhere in the West Indies. Reports from one witness described “a billious fever, it kills in five days; if the patient lives longer it’s only to die in greater agonies from what they call black vomit”.
But Wentworth was still moving in the slow methodical style of a European siege, partly due to a serious lack of qualified engineers in his staff. At this point Vernon’s navy was no help at all. With San Lazaro located further inland from the harbor, none of the navy’s mortars could get close enough to really hammer the fortress the way they had reduced the others. The other part of the problem was that, for all his constant demands that Wentworth show a little more speed, Vernon refused to loan sailors, marines, or even the ship’s heavier guns to the general.
Eslava and Lezo had made Wentworth even more jumpy, and as they approached several other redoubts and found them empty the British sensed a trap. This was not the case, and the longer the British spent hunting shadows the more damage disease wrought on Wentworth’s men. Not that the peninsular Spanish had not paid their own tithe to malaria, they had just done it earlier. Perhaps a third of the garrison had died of disease the previous year, and tropical diseases would still take a chunk out of the defenders. de Lezo himself would die within a few weeks of the siege’s end, but at the very least the Spaniards were not clustered onto poorly sanitized wooden boats in a harbor all the time.
With Vernon nagging in his ear to hurry up, but refusing to actually help at all, Wentworth finally rushed an assault. On April 20th the British charged the fort, carrying ladders and gear to fill in the trenches. The assault was a masterclass in failure, the perfect cherry atop a disastrous campaign sundae. As the attack began at early morning, the Spanish saw it coming and disrupted the first charge with a volley of cannon fire. As the survivors came onwards, they passed at least one concealed trench, and the Spanish poured on flanking fire as Wentworth’s men charged in. Adding insult to crossfiring injury, the survivors who reached the trench at the base of the citadel discovered their ladders were about ten feet too short for San Lazaro’s walls. 600 men and 43 offices were gunned down in two hours of hard fighting before the British fell back.
The epidemic in the British camp and on the ships was now beyond stopping, and Wentworth’s army was no longer a fighting force. The general estimated that by the end of April he had just 3,200 men left fit for duty, a figure that was dropping every day. As many as 50 of Vernon’s ships were also damaged or outright disabled by bad weather and enemy guns. There was nothing for it, the siege was over. If the British invasion was unprecedented, so were the casualties. Of the combined 27-30,000 army and naval personnel an estimated 9,000-11,000 were dead. Another 7,500 were either sick or injured. The Spanish had lost less than a tenth of that, with maybe 600 casualties total.
If the news from Porto Bello had led to near orgasmic celebrations, the hangover from Cartagena was no less intense for Britain. Rather than put blame on their golden boy Vernon, who was already busy shifting any possible blame on to Wentworth, Cartagena was used to attack Walpole. The government was charged with gallivanting off on some foreign adventure halfcocked while the European continent burned. Or alternately, that he had not given Vernon enough men or materiel fast enough to make a difference. Paradoxical blame notwithstanding, the second issue was somewhat fair, most of the units sent to attack Cartagena were raw recruits. Coinciding with another round of electoral shuffling and disputes over the Rotten Burroughs, and it was finally too much for the government. In 1742 the “Robinocracy” came to an end, as two decades worth of corrupt chickens came home to roost on Walpole. He opted to retire, though at King George’s tearful insistence he remained an unofficial advisor to the government.
 Also booze.
 De Zulueta, J. (1992). Health and military factors in Vernon’s failure at Cartagena. The Mariner’s Mirror, 78(2), 127-141.
 A surprisingly common problem. In fairness to all siege engineers, eyeballing the size of a wall is difficult.
 Though perhaps if Walpole had agreed to send crack troops instead of recruits maybe it would have just led to different men dying of disease in front of San Lazaro.