Russia is the only country able to stop the Armenia-Azerbaijan conflict. Will it step up and do so?

People walk in a residential area of Stepanakert that was allegedly damaged by shelling on Saturday.

(CNN)For a while it seemed like they were friends. Russian President Vladimir Putin, the former KGB spy, had managed to slowly pry away one of NATO's most awkward members -- Turkish President Recep Tayyip Erdogan. The pair seemed always on the phone, Turkey was kicked out of the US-led F-35 program for buying Russia's S-400 air defense missile system, and Ankara seemed suddenly closer to Moscow than the Brussels-based alliance.

But how that has changed. After clashing in Syria, backing opposing sides in Libya, and generally finding the other an irritant in their respective bids to capitalize on America's regional withdrawal, Putin and Erdogan are no longer speed-dialing each other. In fact, with the ongoing and escalating fighting between Armenia and Azerbaijan over the enclave of Nagorno-Karabakh, Erdogan has left Putin in perhaps his most complicated spot in years.
Turkey's full-throated backing for the Azerbaijani campaign -- and quite possibly, its facilitation of Syrian mercenaries to back Azerbaijan, something Ankara officially denies -- has led Baku to some swift and brutal progress. Armenia has suggested reviving the old negotiations format, courted US support and vowed to fight on.
    But it does appear to be losing some ground. And as the shelling reaches civilian areas with greater frequency and depth on both sides, there is a deafening silence from Moscow. The regional powerbroker, which neighbors Azerbaijan but has a formal security alliance with Armenia, has used diplomacy to demand the guns fall silent, yet has so far watched this messy chapter in its backyard play out without its discernible influence.
      It is Moscow's move, really, this week.
      Armenia does not look like it has the technical capabilities to match the drones and pace of Azerbaijan's offensive, and is instead widening the conflict, Azerbaijan alleges, by shelling its main cities. This is the moment when traditionally the Kremlin would threaten, cajole or bomb everyone back into the old, established order -- reminding the neighborhood who was its boss for the Soviet decades.
      But it hasn't, and it is unclear why.
        Over the weekend, Putin talked with his security council via teleconference, and, by noon on Monday, the Kremlin website had him talking about the issue, among others, with the President of Tajikistan -- hardly front and center of stemming the prospect of a regional conflagration.
        There is an argument that the Armenian Prime Minister Nikol Pashinyan, who swept to power after a Velvet Revolution in 2018 demanding Western-style reforms, has been exactly the sort of ally Moscow dislikes. Pashinyan has been moving cautiously closer to the European Union, while balancing his country's deep economic ties to Russia. So leaving Yerevan's latest leader to sweat -- and perhaps even lose -- could be punishment for his policies. Remember, Russia even invaded Ukraine's Crimean peninsula after it went too far in its renewed 2014 vigor to befriend Brussels.
        But that message -- of the price of inadequate fealty to Russia -- has perhaps already been heard by Armenia. What's louder is the broader, regional message: that Turkey's ally appears to be winning. It is a risky calculus for Russia: that a nation moving towards the EU -- albeit very, very slowly -- might emerge from this crisis angrier at its pro-EU prime minister, than at its long-term ally -- Russia -- who left it to face the music.