It was most like a Russian built manpad that brought down the Armenian Mi-24. This is a conflict that has Russian sitting on both sides. Publicly, the Russians support (politically and militarily) the Armenians, having a large base within Armenia and training and supplying the Armenian forces and in more than one occasion, even getting involved militarily on the side of the Armenians. The Russians also sell weapons to the Azerbaijan government, as the Russians are one of their primary sources for military weapons.
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