Donbas is decisive in that a comprehensive Russian victory there wouldn’t give them any need to stop. If the price of that victory was low, they may think they could take Odesa too, or even push on to Transnistria to cut Ukraine off from the Black Sea, which would be a huge price for Ukraine to pay… Donbas could put the Russians back on a successful footing or bring them to what is essentially a defeat.
— General Sir Richard Barrons, the former commander of the UK’s Joint Forces Command (The Times: Why Putin dare not lose the battle for Donbas)