When you are concentrated into one while the opponent is divided into ten, you are attack at a concentration of ten to one, so you outnumber the opponent. If you can strike few with many, you will thus minimize the number of those with whom you do battle. Your battleground is not to be known, for when it cannot be known, the enemy makes many guard outposts, and since multiple outposts are established, you only have to do battle with small squads. So when the front is prepared, the rear is lacking, and when the rear is prepared the front is lacking. Preparedness on the left means lacks on the right, preparedness on the right means lack on the left.
Preparedness everywhere means lack everywhere.
The few are those on the defensive against others, the many are those who cause others to be on the defensive against themselves. So if you know the place and time of battle, you can join the fight from a thousand miles away. If you do not know the place and time of battle, then your left flank cannot save your right, your right cannot save your left, your vanguard cannot save your rearguard, and your rearguard cannot save your vanguard, even in a short range of a few to a few dozen miles. So it is said that victory can be made. Even if opponents are numerous, they can be made not to fight.