From what little I could figure out from videos and written reports, I can extrapolate the following with relative certainty:
1. Armenians prepared for a piecemeal positional defence in the mountains and hills. They expected small-scale attacks followed by small-scale counter-attacks to retrieve lost ground. It worked in the North, but in the South, the Azeris managed a breakthrough and massed their forces, relatively safe from artillery bombardment, as Armenian artillery was constantly destroyed by drone warfare.
2. Armenian Air Defence failed big time, and heads should roll. In 1999, Serbia downed dozens of drones far more advanced than Baryaktar, with far inferior tools, while also being pounded by proper aviation, something the Azeris were mostly reluctant to commit. Also, I never once saw proper camouflage. Not so much as camo netting to protect artillery and AA units.
3. While undoubtedly brave to the point of lunacy (the phrase 'heroes fight like Armenians' is not that big of a stretch), for every video I saw where the Armenians were operating calmly under artillery fire, returning fire and passing ammunition, I saw two where they were shooting inshallah style and running about like headless chicken. And it's not like they're the FSA, they know better. It was a failure of discipline and their junior officers and sergeants.
4. No foxholes or block-posts, only big, F***-off trenches made by bulldozers, and very few reserve positions.
5. They underestimated their enemy, big-time. When visiting certain English-language Armenian forums, there is a lot of hubris to be had. Phrases such as 'azeribaboons' and discussions about how they should take back Nakhchevan all the way back in 2016, along with a prevalent attitude of Azeris being cowards are painful to read. Now, that could have been the infamous ballsiness of the diaspora, also very prevalent in the Balkans, but I have a sneaking suspicion that they were common views among the populace, and worse, the military.
6. As others already noted, Armenia did not commit fully. Maybe they thought it wasn't necessary, maybe they thought Turkey would attack Armenia proper, I don't know. But it should have been evident that the Artsakh Defence Army, even if reinforced, cannot deal against what was attacking it.
7. While I doubt the Azeris will ever release the full list of their causalities, I expect them to be at least twice as high as those of the Armenians. They absorbed them and kept pushing, however, something they weren't able to do before.
8. Wherever there were breakthroughs, we saw Azeri T-90s, Matadors, brand new Turkish body armour, and Special Forces. The Romanian AK-wielding conscripts with steel helmets were mostly filmed a bit further back, being ferried by trucks. That leads me to believe that the Azeris adopted the Croat-style strategy of "fix the enemy in place with conscripts and reservists, find a weak spot, pour in elite units). That only works with ample numerical superiority though, something they achieved due to the non-commitment of Armenia.
To summarize, the Armenians are not invincible mountain warriors, Azeris are not incompetent cowards, high-tech warfare does not mean that bloody infantry slogs are not on the menu anymore, and some nations just can't get a break. May God rest the souls of the dead on both sides, especially the ungodly number of 20 and 19 year-olds, and may their uniform-wearing, fist-waving politicians rot in Hell.
