Early the next morning the pirates sacked the place, and made great havoc in the poultry-yards and cattle-pens. They pulled down a number of wooden houses to supply their camp fires. The guns they nailed or sent aboard. The powder they saved for their own use, but some proportion of it went to the destruction of the forts, which, with one exception, they blew up. For some days they stayed there, doing nothing but "roast and eat, and make good cheer," sending the Spaniards to the fields to rout out fresh provisions. While they lay there, Morgan asked "if any banditti were there from Panama," as he had not yet found his guides. Three scoundrels came before him, saying that they knew the road across the isthmus, and that they would act as guides if such action were made profitable. Morgan promised them "equal shares in all they should pillage and rob," and told them that they should come with him to Jamaica at the end of the cruise. These terms suited the three robbers very well. One of them, "a wicked fellow," "the greatest rogue, thief and assassin among them," who had deserved rather "to be broken alive upon a wheel than punished with serving in a garrison," was the spokesman of the trio. He was the Dubosc of that society, "and could domineer and command over them," "they not daring to refuse obedience." This truculent ruffian, with his oaths and his knives and his black moustachios, was elected head guide.

After several days of ease upon the island Morgan sent a squadron to the Main, with 400 men, four ships, and a canoa, "to go and take the Castle of Chagre," at the entrance to the Chagres River. He would not send a larger company, though the fort was strong, for he feared "lest the Spaniards should be jealous of his designs upon Panama"—lest they should be warned, that is, by refugees from Chagres before he tried to cross the isthmus. Neither would he go himself, for he was still bent upon establishing a settlement at Santa Katalina. He chose out an old buccaneer, of the name of Brodely or Bradly, who had sailed with Mansvelt, to command the expedition. He was famous in his way this Captain Brodely, for he had been in all the raids, and had smelt a quantity of powder. He was as brave as a lion, resourceful as a sailor, and, for a buccaneer, most prudent. Ordering his men aboard, he sailed for the Chagres River, where, three days later, he arrived. He stood in towards the river's mouth; but the guns of the castle opened on him, making that anchorage impossible. But about a league from the castle there is a small bay, and here Captain Brodely brought his ships to anchor, and sent his men to their blankets, warning them to stand by for an early call.

The castle of San Lorenzo, which guarded the Chagres River's mouth, was built on the right bank of that river, on a high hill of great steepness. The hill has two peaks, with a sort of natural ditch some thirty feet in depth between them. The castle was built upon the seaward peak, and a narrow drawbridge crossed the gully to the other summit, which was barren and open to the sight. The river swept round the northern side of the hill with considerable force. To the south the hill was precipitous, and of such "infinite asperity," that no man could climb it. To the east was the bridged gully connecting the garrison with the isthmus. To the west, in a crook of the land, was the little port of Chagres, where ships might anchor in seven or eight fathoms, "being very fit for small vessels." Not far from the foot of the hill, facing the river's mouth, there was a battery of eight great guns commanding the approach. A little way beneath were two more batteries, each with six great guns, to supplement the one above. A path led from these lower batteries to the protected harbour. A steep flight of stairs, "hewed out of the rock," allowed the soldiers to pass from the water to the summit of the castle. The defences at the top of the hill were reinforced with palisadoes. The keep, or inner castle, was hedged about with a double fence of plank—the fences being six or seven feet apart, and the interstices filled in with earth, like gabions. On one side of the castle were the storesheds for merchandise and ammunition. On the other, and within the palisadoes everywhere, were soldiers' huts, built of mud and wattle, thatched with palm leaves, "after the manner of the Indians." Lastly, as a sort of outer defence, a great submerged rock prevented boats from coming too near the seaward side.

Early in the morning Captain Bradly turned his hands up by the boatswain's pipe, and bade them breakfast off their beef and parched corn. Maize and charqui were packed into knapsacks for the march, and the pirates rowed ashore to open the campaign. The ruffians from Santa Katalina took their stations at the head of the leading company, with trusty pirates just behind them ready to pistol them if they played false. In good spirits they set forth from the beach, marching in the cool of the morning before the sun had risen. The way led through mangrove swamps, where the men sank to their knees in rotting grasses or plunged to their waists in slime. Those who have seen a tropical swamp will know how fierce the toil was. They were marching in a dank world belonging to an earlier age than ours. They were in the age of the coal strata, among wet, green things, in a silence only broken by the sound of dropping or by the bellow of an alligator. They were there in the filth, in the heat haze, in a mist of miasma and mosquitoes. In all probability they were swearing at themselves for coming thither.

At two o'clock in the afternoon the buccaneers pushed through a thicket of liane and green cane, and debouched quite suddenly upon the barren hilltop facing San Lorenzo Castle. As they formed up, they were met with a thundering volley, which threw them into some confusion. They retreated to the cover of the jungle to debate a plan of battle, greatly fearing that a fort so strongly placed would be impregnable without great guns to batter it. However, they were a reckless company, careless of their lives, and hot with the tramping through the swamp. Give it up they could not, for fear of the mockery of their mates. The desperate course was the one course open to them. They lit the fireballs, or grenades, they had carried through the marsh; they drew their swords, and "Come on!" they cried. "Have at all!" And forward they stormed, cursing as they ran. A company in reserve remained behind in cover, firing over the storming party with their muskets.

As the pirates threw themselves into the gully, the walls of San Lorenzo burst into a flame of gun fire. The Spaniards fought their cannon furiously—as fast as they could fire and reload—while the musketeers picked off the leaders from the loopholes. "Come on, ye English dogs!" they cried. "Come on, ye heretics! ye cuckolds! Let your skulking mates behind there come on too! You'll not get to Panama this bout." "Come on" the pirates did, with great gallantry. They flung themselves down into the ditch, and stormed up the opposite slope to the wooden palings. Here they made a desperate attempt to scale, but the foothold was too precarious and the pales too high. In a few roaring minutes the attack was at an end: it had withered away before the Spanish fire. The buccaneers were retreating in knots of one or two, leaving some seventy of their number on the sun-bleached rocks of the gully.

When they got back to the jungle they lay down to rest, and slept there quietly while the daylight lasted, though the Spaniards still sent shots in their direction. As soon as it was dark, they made another furious assault, flinging their fireballs against the palings in order to burst the planks apart. While they were struggling in the ditch, a pirate ran across the gully with his body bent, as is natural to a running man. As he ran, an arrow took him in the back, and pierced him through to the side. He paused a moment, drew the arrow from the wound, wrapped the shaft of it with cotton as a wad, and fired it back over the paling with his musket. The cotton he had used caught fire from the powder, and it chanced that this blazing shaft drove home into a palm thatch. In the hurry and confusion the flame was not noticed, though it spread rapidly across the huts till it reached some powder casks. There was a violent explosion just within the palisadoes, and stones and blazing sticks came rattling down about the Spaniards' ears. The inner castle roared up in a blaze, calling the Spaniards from their guns to quench the fire—no easy task so high above the water. While the guns were deserted, the pirates ran along the bottom of the ditch, thrusting their fireballs under the palisadoes, which now began to burn in many places. As the flames spread, the planking warped, and fell. The outer planks inclined slightly outward, like the futtocks of a ship, so that, when they weakened in the fire, the inner weight of earth broke them through. The pirates now stood back from the fort, in the long black shadows, to avoid the showers of earth—"great heaps of earth"—which were falling down into the ditch. Presently the slope from the bottom of the gully was piled with earth, so that the pirates could rush up to the breaches, and hurl their firepots across the broken woodwork. The San Lorenzo fort was now a spiring red flame of fire—a beacon to the ships at sea. Before midnight the wooden walls were burnt away to charcoal; the inner fort was on fire in many places; yet the Spaniards still held the earthen ramparts, casting down "many flaming pots," and calling on the English dogs to attack them. The pirates lay close in the shadows, picking off the Spaniards as they moved in the red firelight, so that many poor fellows came toppling into the gully from the mounds.

When day dawned, the castle lay open to the pirates. The walls were all burnt, and fallen down, but in the breaches stood the Spanish soldiers, manning their guns as though the walls still protected them. The fight began as furiously as it had raged the day before. By noon most of the Spanish gunners had been shot down by the picked musketeers; while a storming party ran across the ditch, and rushed a breach. As the pirates gained the inside of the fort, the Spanish Governor charged home upon them with twenty-five soldiers armed with pikes, clubbed muskets, swords, or stones from the ruin. For some minutes these men mixed in a last desperate struggle; then the Spaniards were driven back by the increasing numbers of the enemy. Fighting hard, they retreated to the inner castle, cheered by their Governor, who still called on them to keep their flag aloft. The inner castle was a ruin, but the yellow flag still flew there, guarded by some sorely wounded soldiers and a couple of guns. Here the last stand was made, and here the gallant captain was hit by a bullet, "which pierced his skull into the brain." The little band of brave men now went to pieces before the rush of pirates. Some of them fell back, still fighting, to the wall, over which they flung themselves "into the sea," dying thus honourably rather than surrender. About thirty of them, "whereof scarce ten were not wounded," surrendered in the ruins of the inner fortress. These thirty hurt and weary men were the survivors of 314 who had stood to arms the day before. All the rest were dead, save "eight or nine," who had crept away by boat up the Chagres to take the news to Panama. No officer remained alive, nor was any powder left; the Spaniards were true soldiers. The pirates lost "above one hundred killed" and over seventy wounded, or rather more than half of the men engaged. While the few remaining Spaniards dug trenches in the sand for the burial of the many dead, the pirates questioned them as to their knowledge of Morgan's enterprise. They knew all about it, they said, for a deserter from the pirate ships which raided the Rio de la Hacha (for grain) had spoken of the scheme to the Governor at Cartagena. That captain had reinforced the Chagres garrison, and had sent a warning over the isthmus to the Governor at Panama. The Chagres was now well lined with ambuscades. Panama was full of soldiers, and the whole Spanish population was ready to take up arms to drive the pirates to their ships, so they knew what they might look to get in case they persisted in their plan. This information was sent to Henry Morgan at the Santa Katalina fort, with news of the reduction of the Chagres castle. Before he received it, Captain Joseph Bradly died in the castle, of a wound he had received in the fighting.