Thanks for posting that VH7.
That reasoning is so flawed. Life is war, our Christian walk is war, we wrestle not against flesh and blood but against .... wickedness in high places. And, 2 Timothy 2:3 says, "Thou therefore endure hardness, as a good soldier of Jesus Christ."
I suspect the reason they wrote against chess is because of its inherent mental practice, and also it just gives people another reason to imagine their moral superiority by adding another item to their prohibition list.
Pharisees