We have no way to know if the other general recieved the message, we can only know that the block chain has committed it.
This is the same as a forum or a blog post. We can make a post, but we don't know if the our other party read it.
If the "enemy" army cut off internet access to one general after it responds to attack, even if a message is committed into a block chain, only one general is attacking at first light.
I dream of a world where we don’t create solutions, such as blockchain, and then try to find the problem.