Napoleon became a great emperor because he was short.

Which fallacy is this?

See the response to your above question.

http://www.unc.edu/depts/wcweb/handouts/fallacies.html#7

This is a non sequitur, a false assumption of cause and effect.

false cause

The fallacy in the statement "Napoleon became a great emperor because he was short" is called the "post hoc ergo propter hoc" (Latin for "after this, therefore because of this") fallacy. This fallacy mistakenly assumes that because one thing follows another, it must be the cause of the other thing.

To identify this fallacy, we need to recognize that being short has no direct causal relationship to one's ability to become a great emperor. The greatness of Napoleon as an emperor can be attributed to a range of factors, such as his military strategies, leadership skills, political maneuvering, and the socio-political context of the time.

To avoid this fallacy and arrive at a more accurate conclusion, it is necessary to consider and analyze the multifaceted aspects that contributed to Napoleon's success as an emperor rather than rely on a simplistic and unrelated characteristic like height.