[Antoninus]

As noted above, it is more likely to be a line of communication to existing forces and/or a way to reinforce the border in a crisis. The Chinese use the Kims as their pet psychos for their own purposes. If they intervene, it will be to support the Kim dynasty, not attack it.

Exactly. China's purpose is to make sure that North Korea remains their proxy and is not subsumed by the South. The last thing China wants is a unified Korea aligned with the US. The purpose of the highway is more likely to serve as a conduit to reinforce the North--or to invade the South from the North and thus make Korea a unified proxy state of China.

[tet68]

They are certainly not building it to accommodate
a flood of millions of North korean refugees into
the heart of China.