The drone that slams into a Ukrainian apartment building may have been designed in Iran, built in Russia with Chinese parts and launched alongside North Korean artillery shells.

Retired Rear Adm. Mark Montgomery came back from a couple of weeks in Ukraine with a blunt observation: Ukraine “is fighting Russia, North Korea, Iran and China.”

That is the core argument of “Axis of Aggressors: Countering the Cooperation of China, Russia, Iran and North Korea.” Montgomery wrote the book this summer with Bradley Bowman and Elaine Dezenski of the Foundation for Defense of Democracies.

The authors document 616 instances of security cooperation among the four regimes. These countries are not a formal alliance, and they don’t fully trust one another. They don’t have to. They share a goal, a weaker America, and help each other get there.

Ukraine’s battlefield shows how their cooperation works. North Korea has sent artillery shells and thousands of troops.…