The 16th-century Spanish conquest of the Americas — almost all of South America except Brazil and much of the southern tier of what is now the United States — is one of the extraordinary chapters in human history: extraordinary for the determination, courage and resourcefulness of the conquistadors; extraordinary as well for the violence they inflicted upon the native population, for the zeal with which they promoted Indian and African slavery, for the rapaciousness with which they exploited the region’s abundant natural resources. It is an exciting and engrossing story, but by no stretch of the imagination can it be called a pretty one.

A portion of the story has now been retold by Hugh Thomas, the distinguished British historian whose specialty is Spain and whose many books include “The Spanish Civil War” (1961), “The Conquest of Mexico” (1994) and, most recently, “Rivers of Gold: The Rise of the Spanish Empire, from Columbus to Magellan” (2003), the first in “a series of volumes which I am writing about the Spanish empire.” The present volume is the second in that series, predictably packed to the rafters with Thomas’s celebrated erudition and tireless research but curiously lacking in narrative momentum. It is history for the general readership, an honorable genre in which Thomas has labored to impressive effect for more than half a century (he turns 80 later this year), but “The Golden Empire” is more likely to leave that readership benumbed than spellbound.

Part of the reason doubtless is that Thomas has told much of this story before, most importantly in “The Conquest of Mexico,” with the result that some of this book’s long opening section, “A Tale of Two Cities: New Spain and Old,” reads like a rewrite. Another part of the reason is that here, as in “Rivers of Gold,” Thomas inflicts upon the reader a seemingly endless succession of names, relatively few of which are actuallyessential to his story. Yet another is that the most important phases of the conquest already have been covered far better elsewhere: the first phase in “The Conquest of Mexico,” the second in John Hemmings’s brilliant “The Conquest of the Incas” (1970, revised 1993), the indisputably definitive and ceaselessly readable account of Francisco Pizarro and the defeat of Peru.

Readers of these earlier books will note that in “Rivers of Gold” and “The Golden Empire” more attention is paid to Charles V of Spain, the remarkable “international man” whose ancestors included “one German, a Habsburg, alongside a great gallery of Castilians, Aragonese, and Portuguese,” not to mention “an English forebear, in John of Gaunt,” and a Flemish upbringing. He assumed the Spanish throne while still a teenager and soon thereafter took command of the Holy Roman Empire. He was “magnanimous, liberal, generous,” though he could “bridle at the slightest criticism” and had a messianic view of himself: “He was assured [by courtiers], and came himself to think, that God had chosen him to be the supreme universal monarch. Charles believed that he was the second sword of the Christian Commonwealth, with the Vicar of Christ, the pope, the first.”

“In 1528,” Thomas writes, “the three greatest men of the age were in Spain: Charles, King and Emperor, and his two most important subjects: Hernan Cortes, conqueror of New Spain/Mexico, and Francisco Pizarro, the future conqueror of Peru.” It is easier, I think, to make the case for the greatness of Cortes than that of Pizarro. The former’s defeat of the Aztecs (whom Thomas insists on calling Mexica, “their more accurate designation”) was carried out with immense skill by a small force that overwhelmed the natives because of its far superior weaponry. Cortes was responsible for the brilliant reconstruction of the capital city of Tenochtitlan (Mexico City), and he ruled New Spain with a firm but pliant hand. Thomas’s judgment of him is fair:

‘The Golden Empire: Spain, Charles V, and the Creation of America’ by Hugh Thomas. Random House. 646 pp. $35. (Random House)

“Cortes had transformed the history of Spain and the Americas. Nothing was quite the same again after his astonishing achievement of leading a few hundred Spaniards to triumph over a powerful indigenous monarchy. Matters might easily have gone differently had the Spaniards been led by a less intelligent commander who did not see, as Cortes did, the importance of interpreters; who did not have the gift of serenity in difficult moments, as Cortes had; who did not believe, as Cortes did, that leaving aside gold and glory (important motives certainly), the Mexica would soon find the Christian God and the attendant saints, not to mention the Virgin Mary, irresistible. Cortes’s tactic of kidnapping Montezuma was copied afterward a hundred times, not just in Peru. His skill at transforming the Americas by using a small company of soldiers was an inspiration to other conquerors, who thought that, with a few cavalrymen, they, too, could capture a kingdom.”

Of the other conquistadors, Pizarro was by far the most important and his influence the most lasting. He was “incomparably tough, a good leader, and one loved by those who served with him,” but “like most conquistadors he was quite prepared to be cruel to enemies . . . in a ruthless manner.” That is exactly what he did in late 1532, as he and his tiny band of 168 men reached Cajamarca, the city of Atahualpa, the “last independent Inca [ruler] in Peru.” The Spaniards slaughtered Indians in vast numbers — 2,000 or more according to various reports — and took Atahualpa prisoner. Unlike Montezuma, who died in battle against Spanish forces, Atahualpa was apparently promised his life in exchange for a vast amount of gold and silver, but Pizarro reneged on his promise and had him garroted in the main square of Cajamarca.

Charles V pronounced himself “displeased by the death of Atahualpa since he was a monarch and particularly since it was done in the name of justice,” and the crime — for that it most certainly was — echoed down through the ages, staining Peru and the Andean people to this day. The pattern of violence established by Pizarro was repeated over and over again as other conquistadors stormed through Peru, slashing their way south into Chile, east into Argentina, north into Florida. As Thomas says of one of the most famous of them, “It is hard to sympathize with Hernando de Soto. Yet his plight was genuine. We cannot forgive him his brutalities, nor we cannot forget his multiple tragedies.” If his death in 1542 of “a fever or other infirmity” can be considered a “tragedy,” so be it, but this “reckless, brave, and enterprising” man was, like virtually all the rest, savagely indifferent to the lives of others.

That was the Spanish pattern. The conquistadors came to the New World not to settle and improve it, but to plunder it. They did bring along a few things for which the natives in time were grateful — “mostly the consequence of the wheel, such as pulleys, carts, and wheelbarrows, but also mules and nails, chisels, and iron hammers” — but the effects of their presence in Central and South America were, on balance, more malign than not. Yes, they brought the religion to which the vast majority of Latin America has subscribed ever since, but a great deal of slaughter was carried on in the process of conversion, and more took place as the natives acquired and learned to use the firearms and swords the Spaniards had brought with them.

Bartolome de las Casas, the bishop of the Mexican state of Chiapas who insisted that “the Mexica and the Incas were as intelligent as the Greeks and the Romans” and who spoke out eloquently and often for the rights of the natives, was a lone voice against the majority, which used natives for slave labor and denied them the most basic rights. The conquistadors gave the natives no role in governing the lands that were by right their own and perpetuated the system of encomiendas — grants to individual conquistadors “of the labor and tribute of a certain number of natives . . . living in a specific place” — that helped establish the culture of peonage against which the region struggles to this day. Not much to be proud of.