In all fighting, the direct method may be used for joining battle, but indirect methods will be needed in order to secure victory. Indirect tactics, efficiently applied, are inexhaustible as Heaven and Earth, unending as the flow of rivers and streams; like the sun and moon, they end but to begin anew; like the four seasons, they pass away to return once more.
Sun TzuCarefully compare the opposing army with your own, so that you may know where strength is superabundant and where it is deficient.
Sun Tzu