Sun Tzu Spy Quotations

The end and aim of spying in all its five varieties is knowledge of the enemy; and this knowledge can only be derived, in the first instance, from the converted spy. Hence it is essential that the converted spy be treated with the utmost liberality.

Be subtle! be subtle! and use your spies for every kind of business.

Spies cannot be usefully employed without a certain intuitive sagacity.

They [spies] cannot be properly managed without benevolence and straightforwardness.