It sounded like an echo of Sino-Soviet alliance of the 1950s and 1960s when China's new defense minister, Wei Fenghe, said at a meeting in Moscow this month, "The Chinese side has come to show Americans the close ties between the armed forces of China and Russia."

A full-blown military alliance remains a long ways off, of course, and it is easy to dismiss Wei's remarks as rhetorical posturing. But that would be a mistake, because Wei nonetheless captured an ominous feature of world politics today: the growing alignments between America's various geopolitical rivals.

That alignment is not new, of course: Rogue states and American adversaries such as North Korea, Syria and Iran have cooperated on issues from arms sales to nuclear proliferation for years. What is changing now is that collaboration between America's great-power competitors is increasing, as the threats to the U.S.-led international order also grow.