Invincibility lies in the defense; the possibility of victory in the attack.

Keep their friends close and their enemies closer.

He who knows things, and in fighting puts his knowledge into practice, will win his battles. He who knows them not, nor practices them, will surely be defeated.

Success in warfare is gained by carefully accommodating ourselves to the enemy's purpose.

Those skilled in attack move as from above the nine-fold heavens. Thus they are capable both of protecting themselves and of gaining complete victory.

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.

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