Hostile armies may face each other for years, striving for the victory which is decided in a single day. This being so, to remain in ignorance of the enemy's condition simply because one grudges the outlay of a hundred ounces of silver in honors and emoluments, is the height of inhumanity.

Victory is reserved for those who are willing to pay its price.

Therefore, just as water retains no constant shape, so in warfare there are no constant conditions.

Of all those in the army close to the commander, none is more intimate than the secret agent.

There is no place where espionage is not possible.

The control of large numbers is possible, and like unto that of small numbers, if we subdivide them.

Pretend to be weak, so your enemy may grow arrogant.