The Catholic expeditionary force at Dún an Óir was a mixed body of men who had come a long way to die on this Irish headland. The bulk were Italian and Spanish soldiers raised by Pope Gregory XIII, who saw the Desmond Rebellion as part of a Catholic counter-offensive against Protestant Elizabethan England. They had been sent under the command of Sebastiano di San Giuseppe, an Italian officer. Among them were Irish defenders allied to the cause, along with a handful of women and a captured English priest. Most were soldiers — many of them young, most of them poor, drawn from villages in Italy and Spain that they would never see again. They had been promised they were fighting a holy war. They were not prepared for what was about to be done to them.

After heavy bombardment from sea and shore, the garrison hung out a white flag. The negotiations that followed are still debated. The English afterward claimed the surrender was unconditional — that the defenders had thrown themselves on Lord Grey's mercy. The Italian and Spanish survivors who escaped, and Catholic chroniclers writing later, insisted that terms had been offered: that lives would be spared if the fort was given up. Either way, when the garrison marched out unarmed, the officers were separated from the rank-and-file. The officers were held for ransom. The rest — roughly six hundred men — were taken in groups to a field by the shore where Lord Grey had stationed troops. There they were killed: stabbed, hacked, shot, however the soldiers chose. The work took most of a day.

Cusack's account adds a detail that historians return to with reluctance. A small number of prisoners were spared the immediate massacre and offered their lives if they would renounce their Catholic faith. When they refused, an English ironsmith broke their arms and legs in three places each. They were left lying for a day and night, and then hanged. The cruelty was not random; it was theological theatre, meant to demonstrate the consequences of Catholic loyalty to anyone in Ireland watching. The names of these men are not recorded. Neither are the names of the six hundred others. They were entered into the records only as numbers, occasionally as nationalities, never as people. The monument that now stands at Smerwick — sculpted by Cliodhna Cussen and called Ár gCuimhneacháin Stairiúil (Our Historical Memorial) — was raised in part to give the dead some belated standing as human beings.

Walter Raleigh, then a 26-year-old captain, led one of the killing parties. The poet Edmund Spenser, secretary to the Lord Deputy of Ireland, was almost certainly present; later he defended the massacre in writing as a regrettable necessity of war. Richard Bingham, who would go on to become one of the most ruthless English commanders in Ireland, was also there, though in a letter to the Earl of Leicester he tried to lay the blame on common sailors. Decades later, when Raleigh had lost favor with the crown, prosecutors brought Smerwick against him as a criminal charge. His defense was that he was following orders — what would later be called the Nuremberg defense. The court was unimpressed. Raleigh was eventually executed in 1618, though for treason, not for the men he killed at Smerwick.

The field where the killings happened is called Gort a' Ghearradh — the field of the cutting — and lies near the small headland of Dún an Óir, the Golden Fort. The fort itself has been worn down by four centuries of weather; the earthworks are still visible if you know what you are looking for. The names of those who died here come down to us only in fragments: an Italian named Plinio, a Spaniard named Hercules, a few others. Most are anonymous. They were men who had been told that the journey would be brief and the cause would be holy, and who instead found themselves disarmed, helpless, in a foreign field, watching others die before them and waiting for their own turn. It was a long way from home.