Commenting on the escalating conflict between Armenia and Azerbaijan, the Russian colonel (ret.) Viktor Baranets commented on the question whether Yerevan could use Russia's military base in Gyumri. Baranets wrote that Russia has not signed any document that obligates it to ensure the security of Nagorno-Karabakh. However, if Azerbaijan or Turkey were to invade Armenian territory proper, "this would be an entirely different question."
Below is Baranets' article in Komsomolskaya Pravda:
Viktor Baranets (Source: Topwar.ru)
The Russian Military Base Is An Integral Part Of Armenia's Security System
"The Russian military base is an integral part of Armenia's security system, stated [Armenian] Prime Minister Nikol Pashinyan. He assumed that in 'specific situations' the base's capabilities could be used. According to him, at this current stage of the large-scale war in the Karabakh conflict zone, such a necessity has not yet emerged. 'But situation is unpredictable, and no one can precisely forecast its further development,' said Pashinyan.
"Here immediately the question arises: what 'specific situations' can occur, in which the 'capabilities' of the Russian 102nd military base in Armenia can be used? Let’s consider a few possible options:
"First: Azeri (or Turkish) forces invaded and occupied the legitimate territory of Armenia proper.
"Second: The Air Force of Azerbaijan (or Turkey) carried out missile and bomb strikes on the airfield, where combat aircraft (helicopters) of Armenia and Russia are jointly based.
"Third. Azeri (or Turkish) forces), following military clashes, occupy several areas of Nagorno-Karabakh.
"Of course, there could be countless other options, but we will consider only these for the moment. First of all, we need to look at the documents that define both the military relations between Moscow and Yerevan and the status of our military base in Armenia. The main document was adopted by the Collective Security Treaty Organization (CSTO) back in 1992. Russia and Armenia signed it. Let us read article number 4:
"'If one of the member states is subjected to aggression (armed attack threatening security, stability, territorial integrity and sovereignty), then this will be seen by the member states as aggression against all States - parties to this Treaty.
"'In the event of aggression against any of the participant States, all other participant States will, at the request of that participant State, provide it immediately with necessary assistance, including military, as well as support from their disposal of funds in the exercise of the right to collective defense in accordance with Article 51 of the UN Charter.'
"Everything seems to be very clear. What should Russia do in this situation? - There is a very serious 'problem': Who was the first [to attack] and who was attacked - did Azerbaijan attack Armenia or the reverse? No one can understand this so far, because Yerevan and Baku provide very confusing answers to this question, blaming each other. Secondly, Nagorno-Karabakh is not legally considered to be part of Armenia. And Russia, as the saying goes, did not sign up to protect this territory from anyone whatsoever.
"Now let's talk about our 102nd military base and the possibility of using it in the Azerbaijani-Armenian armed conflict. Here, too, we need to look at the documents, and first of all at the Russian-Armenian agreement on the status of our base. It reads: 'The Russian military base during its deployment on the territory of Armenia, in addition to the functions of protecting the interests of Russia, ensures the Republic of Armenia's security in conjunction with the armed Forces of Armenia...'
"Pay attention to the words – 'ensures... the security of the Republic of Armenia.' There is nothing about ensuring the security of Nagorno-Karabakh. Because (I repeat) it [Nagorno-Karabakh] is not legally a territory of Armenia. Thus, Russia has no legal right to use its military base to protect Nagorno-Karabakh. However, if Azerbaijan (or Turkey) will enter into the Armenian territory - it would be a whole other question. In this case, the capabilities of the 102nd Russian military base can be harnessed. And even more so if someone decides, let’s say, to bomb the Russian military base in Gyumri or the Erebuni air base, where Russian and Armenian planes and helicopters are stationed together."
 Kp.ru, September 30, 2020.
See MEMRI Special Dispatch No. 8887, Armenian Expert Azadian: Russian Military Base In Armenia Is A Deterrent Against The Turkish Threat; Turkey Foments Crises So It Can Intervene In, Or Exploit, Destabilized Regions In Order To Expand Its Empire, August 11, 2020; MEMRI Special Dispatch No. 8886, Armenia-Azerbaijan Tensions – Moscow-Based Expert Krylov: 'The Turkish Military Presence In Azerbaijan Has Become Permanent' And Strives For Constant Expansion; Erdoğan's Policy Aims To Increase Turkey's Influence – From North Africa To China's Borders, August 10, 2020; MEMRI Special Dispatch No. 8875, Russian Military Expert Pavel Felgenhauer: Russia Will Defend Armenia From The Turks; If Necessary, Russia Will Save Armenia With A Nuclear Strike, August 3, 2020; MEMRI Special Dispatch No. 8864, Kommersant Columnist Yusin: Erdogan Is Pouring Kerosene On The Territorial Dispute Between Armenia And Azerbaijan, July 27, 2020; and MEMRI Daily Brief No. 226, Where Will Erdoğan Strike Next?, by Alberto M. Fernandez, August 4, 2020.