The skillful warriors in ancient times first made themselves invincible and then awaited the enemy's moment of vulnerability. Invincibility depends on oneself, but the enemy's vulnerability on himself. It follows that those skilled in war can make themselves invincible but cannot cause an enemy to be certainly vulnerable. Therefore, it can be said that, one may know how to achieve victory, but cannot necessarily do so.
Invincibility lies in the defense; the possibility of victory in the attack. Defend yourself when the enemy's strength is abundant, and attack the enemy when it is inadequate.*
Those who are skilled in defense hide themselves as under the most secret recesses of earth.
Those skilled in attack flash forth as from above the topmost heights of heaven.
Thus, they are capable both of protecting themselves and of gaining a complete victory.
Other translators offer different interpretations of invincibility in the attack and defense:
*So we see that the great general can protect himself from giving the enemy an opportunity for victory, but he cannot make the enemy susceptible to defeat. Brian Bruya
*Invincibility is a matter of defense, vulnerability is a matter of attack. Defense is for times of insufficiency, attack is for times of surplus. Thomas Cleary
