I stumbled across this tidbit of history in the above mentioned book. Horwitz is describing the Spanish Conquistador, Coronado's first incursion into the present day US. This passage describes his search for the semi-imagined seven cities of Cibola (and of course, gold! gold! gold!) which it turns out was a Pueblo settlement in present day New Mexico (which had only a measly bit of turquoise.)
"Coronado didn't record his first impressions of Cibola. Instead, he describes a curious ritual the Spanish performed outside the pueblo's walls. Coronado sent several soldiers, a friar, and an Indian interpreter ahead to deliver the edict called the Requerimiento, or Summons. Drafted three decades earlier by a Spanish jurist, the document was part of the Crown's tortured attempt to define "just war" against Indians: a sort of sixteenth-century Geneva Convention. Conquistadors carried copies of the Requerimiento all over the Americas and were commanded to read it to Indians before commencing battle.
The proclamation opened with an abridged history of the world: God's creation of heaven and earth; Adam and Eve; St. Peter and the papacy. It also explained that the pontiff in Rome had authorized Spain's claim to the New World, a grant recorded in various document. 'These you may view if you wish,' the Requerimiento assured its Indian audience. Then came the summons. Natives who peacefully accepted the Spanish Crown as "king and lord" would be welcomed "with complete affection and charity," and extended many privileges. Indians should pause to consider this generous offer, taking as much time as "is reasonable."
However, if they delayed, or refused to submit, the consequences would be immediate and awful. "I assure you that, with the help of God, I will attack you mightily. I will make war against you everywhere and in every way... I will take your wives and children, and I will make them slaves... I will take your property. I will do all the harm and damage to you that I can." And further: :I declare that the deaths ind injuries that occur as a result of this would be your fault an not his Majesty's nor ours."
The document concluded with the chilling legalism of Spanish conquest; a notary required to be present at the scene, signed an affidavit attesting that the edict had been pronounced. In modern terms, the Spanish thereby affirmed that natives had been read their Miranda rights. In practice the Requeriminto was more akin to last rites-- a death sentence delivered in language Indians couldn't possibly comprehend, in the name of forces they couldn't possibly imagine. Who was "God, Our Lord"? The "Pope"? The "exalted and powerful monarch" of a place called Castile and Leon?
As if the Requerimiento wasn't a bald enough sanction for slaughter, it was often read without an interpreter present, or was delivered from a distance of several miles, or uttered at night while Indians slept, unaware of an impending attack. The Dominican friar Bartolome de Las Casas declared that he didn't know "whether to laugh or cry" at the absurdity of the document." (Henry Holt & Co., NY; 2008: p.144.)