Only in set piece battles against entrenched forces. You are seriously over-estimating Japanese artillery.
isn't a siege the definition of a set piece battle against entrenched forces?

You're missing the point. The Koreans don't have to overrun the Japanese positions. They just have to cut it off. Could the Japanese have stopped the PVA's 2nd and 3rd Offensives?

Come to think of it, how would the IJA stop 200,000 Koreans armed with Chinese artillery storming over the Yalu using Mongol/PVA maneuver?
i don't know if the PVA is the correct analogy to use here. yeah, the japanese would probably be beaten against a battle-hardened force that had a lot of US training and equipment and even more Soviet training and equipment.

but a 200K KPA new to combat outside of small unit actions, doing a hostile river crossing?

i can see guerrilla warfare but the idea that Korean guerrillas are going to assemble a maneuver army...i mean, the VC couldn't and didn't do that, it took regular units of the North to beat the Americans and the South Vietnamese.

i understand the Japanese are essentially a WW1 army but for all that, they were good enough to essentially bleed the KMT dry even after the KMT got enormous amounts of US monies and supplies. can't see Koreans posing half the difficulties the Chinese posed.