Synthetic DNA.
It was the last city left for conquering Luhansk. It had no strategic or tactical value, it's value was only political. Zelensky didn't want to give up the last stronghold in Luhansk.
Even today, the Slovyansk-Kramatorsk region holds no military value. But withdrawing from there would mean Donbas ends up under Russian control without a fight. So even that's another political decision. Ukrainian and Western military experts have argued for moving the frontline to the Dnipro-Kharkiv line, ie, the Dneiper River. So, basically, what it means is all the Ukr troops who are gonna die fighting to keep Donbas are gonna die in vain. But pulling back to the main river will complicate Russia's offensive significantly. So that's the Mykolaiv-Zapo-Dnipro line in the south. Going east to Kharkiv. Of course, if Kharkiv falls, they will have to completely pull back across the river, or at least up to Poltava in the center.
If the Russians mobilise, then the UAF will have to fall back to the river and sue for peace. Of course, by then Mykolaiv and Odessa would have fallen too. The only question then is where the Russians will actually stop. 'Cause after Popasna fell, holding Donbas became meaningless to the UAF. In Lysychansk, the UAF has completely lost the will to fight, and these are their best guys.
