The Houthis, the Iran-backed militia that controls much of Yemen, have disrupted the global economy by firing on commercial ships traveling through the Red Sea. But the Houthis have made some exceptions: Ships from China and Russia are allowed to pass without being attacked.

This policy, formalized with a diplomatic agreement last month, is the latest sign that the world has entered a new period of great power politics. On one side is the largely democratic alliance — including the United States, Japan, South Korea and Western Europe — that has dominated global affairs since the demise of the Soviet Union. On the other side are China, Russia, Iran and North Korea as well as Iran-backed groups like the Houthis.

These authoritarian powers “are more and more aligned,” Jens Stoltenberg, the head of NATO, the Western alliance, told the BBC this week. “They support each other more and more, in very practical ways.”

In today’s newsletter, I’ll explain how the emerging alliance is shaping the world and why experts are anxious about the future.