Iraq was supposed to be able to defeat Iran easily (chaos in Iran, surprise, modern arms and tactics, 10,000 tanks, etc., etc.). It didn't work out that way.

We don't really know how it would play out on the ground.

Given time, we would win. But how long would it take? Korea has had decades to prepare for the war they have said is coming (tunnels, hardening, etc., etc.).

Cheers,
Scott.