In fact, Lord Cheng sent a signal to that person, but it's uncertain if he can understand the message.
It's his first time meeting that person, they're not familiar.
If the other person is sharp, he'll naturally go back and inform General Shen. If he fails to see it, then General Shen will be in danger.
Thinking of this, Lord Cheng couldn't help but feel anxious.
He wasn't afraid of dying, if he could get the message out, dying would earn the Cheng Family a reputation for heroism. But he's worried his death would be utterly meaningless.
Moreover, a troubling aspect is...
"The people of the black market not only want those twenty thousand troops, but also many prisoners from the southwest. The southwest is an exile area, where many vicious criminals exist; they exploit the Emperor's unwillingness to grant a royal pardon and make a big issue out of it, trying to recruit these people to strengthen their own force."
