Oh hun, you're so silly

You’re right. There are other factors. Factors that a wall did nothing about. A construction project taking many man hours and diverting huge sums of money to solve a problem that ultimately a wall could not solve. If ants invade your home so you buy a gun and shoot any ant coming through the front door- but then you still have ants in your cupboard- well hell. The gun stopped them at the front door but I guess that wasn’t the big problem or the best tool to fix the problem was it?

It certainly delayed the Mongols and allowed enough warning for cities to prepare their surrender, but without a large and well trained military, more sophisticated long range communication, and half-decent leadership, the Song dynasty never stood a chance.

Very true.

I guess they should have built that city on rock and roll