The master plan called for a landing near Portobelo, the capture of the Spanish settlement there, a march across the Isthmus and then a surprise attack on Panama City, the crossroads of two continents. But they had an ambitious ulterior motive. The buccaneer force expected to capture enough ships in the port of Panama to form a South Seas Buccaneer Navy and launch a brilliant era of plundering along the coasts and attacking Pacific shipping.

The vision of Manila galleons, ablaze with treasure crammed in the hold and piled high on the decks, shimmered before them as they slogged sixty miles through rough country toward Portobelo from their anchored ships. Three days they had no food and many of the men had their "feet cut with rocks for want of shoes," but on the fourth day spirits soared as the church spires of Portobelo appeared ahead of them. Once again, the Spanish were caught with their guard down. The town was taken, sacked and abandoned in haste since the buccaneers feared the arrival of reinforcements. Each looter received a measly share of one hundred pieces of eight; disappointing but not depressing since greater prizes lay ahead.

Captain Sawkins and Captain Harris joined the buccaneers as they began their trek across the Isthmus with a contingent of Indian guides. Two captains and a number of men left to guard the buccaneer fleet and the 331 who were to march each received several "doughboys" or large loaves of bread and orders to drink from the rivers. Each buccaneer was armed with a rifle, pistol, and a sword, and they marched in military formation, each company falling in behind its captain and standard. The first of these seven led by Captain Sharp whose flag was red with white and green streamers.

The Indians told them of a town called Santa Maria, inland on a river which emptied into the Pacific and the Golfo De San Miguel. It was, according to their informants, a place where gold gathered in the surrounding mountains was stored by the Spaniards for transport to Panama. Along the way they cracked open the river rocks and found the sparkle of gold. At Santa Maria they found abundant provisions and some river boats but very little gold. They cursed the luck that made them miss three hundred pounds of refined gold which had been shipped to Panama three days before they arrived. They earned the gratitude of the Indian King of Darien by freeing his pregnant daughter who had been abducted and raped by a Spanish soldier.

The buccaneers elected Coxon as their chief and they pressed on for Panama in thirty six captured boats and rowed or sailed to the Pacific, guided by the Spaniard who had dishonored the Darien princess who offered to lead the pirates to the very bedchamber of the governor of Panama.

Panama turned out to be farther than the adventurers had imagined, and the way was paved with mishaps. Torrential rains turned the river into a violent adversary, booby trapped with logs and shoals. Ringrose wrecked. was captured, and escaped slaughter when the soldier from Santa Maria who had been in his canoe when it wrecked told his countrymen of how kind the English pirates had been in saving him from the wrath of the Indians. Ringrose caught up with the buccaneers and eventually they came within sight of the city. They spied eight ships riding at anchor off the little Isla Perico near Panama. Five were great treasure galleons from Peru and the others were Barcos De La Armadilla, guard ships.

Unfortunately for the buccaneers, the element of surprise was lost. The Spaniards, hearing of the buccaneer march, had concentrated their entire force of 228 men on the convoy ships, leaving the galleons unmanned. The three warships made straight for the buccaneer fleet of puny canoes and two larger but sluggish hollowed out craft which they had seized a couple of days earlier. The odds were with the Spanish, for not only did they have superior ships and arms, but the majority of the buccaneers were missing having gone to search for fresh water. Yet once again the amazing fearlessness and drive, characteristic of sea rovers down through the ages, spurred the buccaneers on to victory in a gory battle. They took the warships, slaying two thirds of the Spanish, black and mestizo crews. "Their blood ran down the decks in whole streams, and scarce one place in the ship was found that was free from blood," wrote Ringrose of the warship on which seventy seven blacks had fought under the command of Don Francisco De Peralta, an old Spaniard from Andalusia. Next, the buccaneers boarded the empty galleons, making the largest one, the Santissima Trinidad, their flagship.

The buccaneers were at their best battle and were undaunted by the overwhelming enemy forces, however, they were often undone by internal bickering. There was quibbling over the division of labor and the sharing of the booty. Within a few days of the battle Captain Coxon, who had been called a coward by some, left with his men and returned to the Caribbean the way they had come. He was an envious, bad tempered man who had crossed swords with several of the buccaneer leaders and no one was sorry to see him leave. A warrant for the arrest of Coxon, Sharp, and the others who had sacked Portobelo had been issued in Jamaica by Lord Carlisle, who no doubt was embarrassed by what the "log wood cutting" expedition he sanctioned had turned into. Three of Coxon’s men were apprehended and imprisoned. But Coxon had such influential friends on the council that when he returned to Port Royal, after pirating a bit around the Islas San Blas, he wasn’t punished but instead sent by the council to hunt a troublesome French pirate named Jean Hamilton.

The buccaneers who remained behind, in Panama, elected a young and popular Sawkins as their leader. They cruised along Panama’s Pacific coast, taking a number of ships including one laden with 2,000 jars of wine, 50 jars of gunpowder and 51,000 pieces of eight being sent from Trujillo to pay the garrison in Panama. They took merchant ships, too selling the Africans they found aboard to the Spanish merchants, ever willing to deal in contraband. Those prisoners they thought of no value were put on captured ships whose masts and sails had been destroyed and set adrift. The buccaneers made their base for awhile on Isla Taboga. When the governor of Panama sent a message inquiring why they had come to this part of the world, Sawkins answered "we came to assist the King of Darien, who was the true Lord of Panama and all the country thereabouts." If the governor would sent fifty pieces of eight for each buccaneer, a thousand for each commander and desist from annoying the Indians, allowing them the power and freedom that they were due, then the English would be happy to leave. Otherwise, warned Sawkins, they would stay and inflict as much damage as they could. To query from the governor as to whose commission they carried, the brash buccaneer replied that "we would come and visit him at Panama and bring our commissions on the muzzles of our guns, at which time he should read them as plain as the flame of gunpowder could make them."

All this blustering came to little, for provisions ran so low that Sawkins was forced by his men to sail on even though leaving Taboga meant forfeiting the capture of a ship carrying 100,000 pieces of eight which was due in Panama momentarily from Peru. On the way to the pearl fishery islands of Cayboa, which today is the penal colony known as Coiba, the buccaneers attacked the town of Pueblo Nuevo. For once the Spanish were defensively prepared and Sawkins was killed as he ran up a breastwork thrown up before the town.