vacuumflower
USSR’s central government was on the Azeri side in the first war and its military did participate in ethnic cleansing, and not as some expulsion, but outright mass murders. After USSR ceased to exist, such entity as CIS military (shortly abolished afterwards) did participate on Azeri side, with large input into their 1992 offensive (very successful, they’ve took about half of NKAO, including all of Martakert).
What I mean is that war started before USSR ceased to exist. With first pogroms against Armenians, then fighting between police and volunteers on the Armenian side and police and some Soviet military on the Azeri side (there’s the notable exception of what Azeris call “the Black September”, when Soviet troops under general Lebed’ entered Baku and stopped the pogroms against Armenians, Azeris consider that a tragedy). Already during the conflict national militaries of Armenia, NK and Azerbaijan were created. Both Armenia and Azerbaijan frankly failed that process (Armenia proper’s little participation in the war involves some catastrophes due to bad organization, similar to Azerbaijan’s, though it did take Karvachar and protect its borders in general), while NK managed to do it sufficiently well, still it wasn’t such a clear Armenian victory, hence the ceasefire.