Found: Si-Fi planet-conquering adventure: last page twist: actually Cortés and America

(So I actually have only heard about this book. I wrote down the title because I thought it sounded interesting, but then lost the note I wrote the title on.)

Very cleverly written to make the reader think it is a cool/fun/adventure book about conquering a new planet with space ships, but then on the last page the author reveals it is actually a historical account of Hernán Cortés, with the whole 'things make more sense why it was written/occurred that way' on the second read.

Possibly written to give the reader a way to view events with less preconceived notions?

Would appreciate if anyone knows the name/author of the book, (and if it is worth finding a copy).

Despoilers of the Golden Empire by Randall Garrett?

https://en.wikipedia.org/wiki/Despoilers_of_the_Golden_Empire

I think that is it.
Thanks!

Edit: Just skimmed it and the authors end note: definitely it.
Thanks again.

and for anyone interested, as MissSquish will probably tell you
it is actually about Francisco Pizarro, the Conqueror of Peru, not Cortez.

Touchstone: Despoilers of the Golden Empire