New Delhi, May 31 -- In recent weeks, China, America and Russia have been engaged in high-level diplomacy. US President Donald Trump visited China. His trip was quickly followed by a visit from Russian President Vladimir Putin to Beijing.Chinese President Xi Jinping is expected to travel to America soon, while Putin is likely to visit New Delhi for the Brics summit in September.

With the Iran conflict dominating headlines, most commentators are interpreting the US-China meeting through the prism of a possible settlement in West Asia. That deal will eventually happen.

Yet, the broader US-China engagement may prove far more consequential. In many ways, it echoes the famous US-Soviet detente of the 1980s that began with the unratified Salt...