Q. How would you style Napoleon’s name in something like “They researched the tin buttons on the uniforms of soldiers in Napoleon’s army.” Merriam-Webster has “Napoléon I” under the “Bonaparte” entry but “Napoleon I” under the “napoleon” entry. Encyclopaedia Britannica has “Napoleon I” as its first entry. CMOS 5.128 has “if Napoleon was in fact poisoned” as an example. So should my example sentence have an accent on “Napoleon,” include the “I,” or include “Bonaparte”?
A. Although fidelity to a person’s name is an important consideration, Napoleon Bonaparte entered the English vernacular long ago—without the accent. So, whereas “Napoléon” is the correct spelling of that name in French (where the accent is mandatory), there’s no need to use the French spelling in an English-language context.
As for the Roman numeral, add it only when needed for clarity—for example, to distinguish Napoleon I (or, in French, Napoléon Iᵉʳ) from Napoleons II and III. (Superscripts like the one in “Napoléon Iᵉʳ” are generally retained in an English-language context; see CMOS 11.30.)
As for “Bonaparte,” you can usually add that at your first mention of Napoleon, who is otherwise typically referred to by his first name.