The strategic relationship between Moscow and Beijing makes the problem even more dangerous.
China has provided Russia with dual-use components that support its military-industrial base. Russia can offer China battlefield knowledge, advanced military technology and lessons from years of sustained warfare. The two countries also conduct joint exercises and share a desire to weaken American influence.
Their interests are not identical, and neither government fully trusts the other. But a formal alliance is unnecessary.
China benefits when Russia absorbs American resources in Europe. Russia benefits when China forces the United States to concentrate ships, aircraft and missiles in Asia. Every American weapon sent to one theater is a weapon unavailable in the other.
This creates a strategic form of cooperation even without coordinated battle plans.