The acute security flare-up on the Korean Peninsula will show whether an acceptable modus vivendi can be found between Washington and Beijing.

The two nuclear-armed countries are pointing at each other their most lethal strategic weapons while trying to resolve the legacy of an inconclusive war they fought, with the help of their allies, on behalf of the South and North Koreas from June 1950 to an armistice in July 1953.

The immediate causes of hostilities have changed, but the fundamental reasons for the U.S.-China confrontation along the 38th Parallel North remain the same. China wants the U.S. out of South Korea – indeed out of Asia, as was constantly repeated during American intelligence gathering and freedom of navigation maneuvers around China's contested maritime borders.

More recently, China has become hugely worried about American missile shield installations in South Korea and Japan. Beijing claims that the shield is compromising its security, hinting even that its nuclear arsenal could be paralyzed. Beijing's alarm level will also go up another notch as Seoul got Washington's agreement to deploy American strategic military assets in South Korea.

And here is the deal: Washington wants China to help in forcing North Korea to immediately and verifiably give up its nuclear weapons and their delivery vehicles with debilitating economic sanctions.