Spies cannot be usefully employed without a certain intuitive sagacity.

Victory comes from finding opportunities in problems.

Secret operations are essential in war; upon them the army relies to make its every move.

There are not more than five musical notes, yet the combinations of these five give rise to more melodies than can ever be heard.

Of all those in the army close to the commander none is more intimate than the secret agent; of all rewards none more liberal than those given to secret agents; of all matters none is more confidential than those relating to secret operations.

To perceive victory when it is known to all is not really skilful. Everyone calls victory in battle good, but it is not really good.

War is a matter of vital importance to the state.