12. On open ground, do not try to block the enemy's way.
[Because the attempt would be futile, and would expose the
blocking force itself to serious risks. There are two
interpretations available here. I follow that of Chang Yu. The
other is indicated in Ts`ao Kung's brief note: "Draw closer
together"--i.e., see that a portion of your own army is not cut
off.]
On the ground of intersecting highways, join hands with your
allies.