XIII: On The Use Of Spies
A major military operation is a severe drain on the nation, and may be kept
up for years in the struggle for one day's victory. So to fail to know the
conditions of opponents because of reluctance to give rewards for
intelligence is extremely inhumane, uncharacteristic of a true military
leader, uncharacteristic of an assistant of the government, uncharacteristic
of a victorious chief. So what enables an intelligent government and a
wise military leadership to overcome others and achieve extraordinary
accomplishments is foreknowledge.
Foreknowledge cannot be gotten from ghosts and spirits, cannot be had by analogy, cannot be found out by calculation. It must be obtained from people, people who know the conditions of the enemy.
There are five kinds of spy: The local spy, the inside spy, the reverse spy, the dead spy, and the living spy. When the five kinds of spies are all active, no one knows their routes - this is called organizational genius, and is valuable to the leadership.
Local spies are hired from among the people of a locality. Inside spies are hired from among enemy officials. Reverse spies are hired from among enemy spies. Dead spies transmit false intelligence to enemy spies. Living spies come back to report.
Therefore no one in the armed forces is treated as familiarly as are spies, no one is given rewards as rich as those given to spies, and no matter is more secret than espionage.
One cannot use spies without sagacity and knowledge, one cannot use spies without humanity and justice, one cannot get the truth from spies without subtlety. This is a very delicate matter indeed. Spies are useful everywhere.
If an item of intelligence is heard before a spy reports it, then both the spy and the one who told about it die.
Whenever you want to attack an army, besiege a city, or kill a person, first you must know the identities of their defending generals, their associates, their visitors, their gatekeepers, and their chamberlains, so you have your spies find out.
You must seek out enemy agents who have come to spy on you, bribe them and induce them to stay with you, so you can use them as reverse spies. By intelligence thus obtained, you can find local spies and inside spies to employ. By intelligence thus obtained, you can cause the misinformation of dead spies to be conveyed to the enemy. By intelligence thus obtained, you can get living spies to work as planned.
It is essential for a leader to know about the five kinds of espionage, and this knowledge depends on reverse spies, so reverse spies must be treated well.
So only a brilliant ruler or a wise general who can use the highly intelligent for espionage is sure of great success. This is essential for military operations, and the armies depend on this in their actions.