I did not see this one in the quotes.

"War is therefore an act of violence intended to compel our opponent to fulfill our will." - Karl Von Clausewitz

"War is a duel at an extensive scale." - Karl Von Clausewitz

Other quotes from Clausewitz:

"Courage, above all things, is the first quality of a warrior."

"If the leader is filled with high ambition and if he pursues his aims with audacity and strength of will, he will reach them in spite of all obstacles."