According to Article 4 of CSTO
If one of the Member States undergoes aggression (armed attack menacing to safety, stability, territorial integrity and sovereignty), it will be considered by the Member States as aggression (armed attack menacing to safety, stability, territorial integrity and sovereignty) to all the Member States of this Treaty.
In case of aggression commission (armed attack menacing to safety, stability, territorial integrity and sovereignty) to any of the Member States, all the other Member States at request of this Member State shall immediately provide the latter with the necessary help, including military one, as well as provide support by the means at their disposal in accordance with the right to collective defence pursuant to article 51 of the UN Charter.
So, During the Second Nagorno-Karabakh War (in whichwhich Azerbaijan won), Hashave any of the CSTO members given an official reason for not following what's laid down in theory ? What were the practical constraints in providing military aid to Armenia (for Russia especially)?