The crossword solution for the term 'KNOW THY ENEMY' is a three-letter word, 'THY'. This phrase is derived from the Latin phrase 'Nosce te ipsum', which translates to 'KNOW thyself'. It is often used as a reminder to be aware of one's own strengths and weaknesses before attempting to understand or confront an adversary. The phrase is also used to emphasize the importance of understanding one's opponents in order to gain an advantage in any situation.