successful war brings evil in its train. Wu remarks that “few are those who have gained power on earth by many victories,” and he is insistent that war should not be undertaken until a careful comparison of the two sides shows that victory is certain; and he adds, “The army which conquers makes certain of victory and then attacks, while the army that is defeated fights in the hope of success.”
Hence the importance they assign to intelligence of the enemy, and to the spy; and as the sages dealt with war between members of the same race, the work of spies was greatly facilitated. The spy was treated with great honour by his countrymen, and the fact that many of the national heroes of China were spies, shows that the part that they played was not forgotten. They frequently toiled for years, and rose to high rank in the enemy’s service; and thus, by wrong counsel and by spreading mistrust in his ranks, they became a two-edged sword in the hands of the general. "Wonderful, indeed, is their power,”
