Who said "Knowledge of the enemy is half the battle."?

This quote is attributed to Arrow.

Knowledge of the enemy is half the battle. - Arrow

"Knowledge of the enemy is half the battle."

Arrow Knowledge

"My name is Oliver Queen. After five years in hell, I have come home with only one goal: to save my city."

"I'm not the man I was."

"You have failed this city."

"I'm a monster."

"We're not just after treasure. We're preserving history."

"The mind is humanity's greatest tool."

"A tidy room reflects a tidy mind."

"You can learn a lot about a person by how they keep their space."