TEHRAN, Iran — On Nov. 1, Russian President Vladimir Putin went on a working visit to Tehran for the second trilateral Caspian Summit. His busy one-day agenda included encounters with Iranian Supreme Leader Ayatollah Ali Khamenei, President Hassan Rouhani and Azerbaijani President Ilham Aliyev.

This is Putin’s third visit to Iran — the last time being November 2015, two months after the start of Russia’s military campaign in Syria.

Although this time the issue of energy cooperation was central at the trilateral meeting, it was Putin’s discussions of Syria with Khamenei and Rouhani that for many outside observers was the most intriguing part of the talks.

Over the course of the Syrian war, Russia and Iran have been crucial to one another both politically and on the ground, with intelligence sharing and the number of military contacts unprecedented in the modern history of the two countries. Yet Moscow and Tehran don’t always share similar views on the future composition of Syria’s government, the role of the Kurds, the fate of President Bashar al-Assad or the tacit rivalry for control over mineral resources in some parts of the country. Top all of that off with the deep-seated historic distrust fueled every time Russia is in contact with any of Iran’s archenemies — Israel, Saudi Arabia or the United States — or works with the Syrian opposition outside the framework of the Astana peace talks.