Can a general who knows calligraphy be called both civil and military?

You can't. Being both civil and military means being able to be literate and martial, and outstanding in literary talent and martial arts. Literary talent refers to the ability to write poetry, and calligraphy does not belong to writing. A general who knows calligraphy can't be said to have both culture and martial arts. General is a general term for senior military generals. Different dynasties and countries have different specific references. China often served as a senior military attache, a military official and even a knight in ancient times. In modern times, it is often used to address general officers in the army.