In July 2019, during the twilight of the first Trump administration, the Defense Department kicked Turkey out of the F-35 joint strike fighter program. While analysts can debate the wisdom of including Turkey in the F-35 program to start with, its expulsion was warranted: By purchasing Russia’s S-400 anti-aircraft missile system, Turkey put NATO at risk in two ways.

For a start, integrating the S-400 into Turkish air defense, as Turkey did last week, betrays NATO codes and systems. Even if the S-400 remained an independent, self-contained system, its tracking of Turkey’s F-35s could enable Russian engineers to identify weaknesses and vulnerabilities. That Turkey seeks to build its own domestic defense industry and can reverse engineer any advanced technology it is given makes the idea of selling the F-35 even more self-defeating.