Last month, when President Vladimir Putin of Russia announced plans to sell a powerful anti-missile system to Iran before the lifting of international sanctions, Israel was quick to join the U.S. in expressing shock and anger.

But behind the public announcements is a little-known web of arms negotiations and secret diplomacy. In recent years, Israel and Russia have engaged in a complex dance, with Israel selling drones to Russia while remaining conspicuously neutral toward Ukraine and hoping to stave off Iranian military development. The dance may not be over.