When, if ever, is it acceptable to change known facts about the lives of real people for the purposes of fiction?
Some people’s lives are so well documented that it would be difficult, if not impossible, for a novelist to change aspects of them.
What about the less well known?
I recently read a historical novel in which the central character was fictional but many of the background, secondary characters were real people. Some were prominent - members of the royal family, members of the government of the time. As far as I could tell, the roles they played in the novel didn’t conflict with any known facts about their actions or beliefs.
One was obscure. Probably few people would know that he really existed. I only know because I happen to have come across him when reading the history of my own county. It was clear that the author was indeed referring to this man and hadn’t just happened to pick the same name for her fictional character.
The author changed the date, place and manner of his death. In fact, she made him the victim of the murder that the central character had to solve.
Does it matter? Does it matter more or less because this man was relatively unknown? The author did retain the man’s quite extreme political and religious opinions, which is perhaps more important than the bare facts about his death.
However, I don’t see why the author could not simply have invented a character with similar beliefs and history to the man she used, whom she could have killed in any way she pleased.
It’s not always possible to replace a real person with a fictional character. Some people’s contribution to history is unique - one could not invent a character to fill the role of Drake, or Cromwell (either of them!) or Wellington or Churchill.
But where lesser people are concerned I think it would be preferable to create a fictional captain and ship to play a part in the Armada campaign rather than trying to make a real captain and ship fit the purposes of the plot. Better to have a fictional Member of Parliament, or a fictional army officer.
The author is then free to develop character and plot as he or she pleases, rather than having to fit the plot to the known facts about the person's life and personality. Or, as in the case above, ignore the known facts.
Development of character and plot is what fiction writing is about, after all.