Odesa is highly-prized by both sides, reports Senior International Correspondent John Irvine
This is a romantic roguish city. Its history, architecture and cosmopolitan vibe combine to make it quite the prize in this war.
Add the fact that Odesa is Ukraine’s biggest port, and that its fall would leave this country landlocked, and you can see just how high the stakes are here.
The Russian Army units that came out of Crimea and turned west towards Odesa have been the most successful of the war.
It was they who took Kherson, the first and only city to have fallen so far. Next in their firing line was Mykolaiv, where the Ukrainians are putting up stubborn resistance.
Some Western analysts think the Russians may be preparing to circumvent Mykolaiv so keen are they to push on and attack Odesa.
The hedgehog anti-tank defences in front the Odesa Opera House look just as out of place as they would in front of the Royal Albert Hall.
But they are part and parcel of an elaborate defensive line put in place by one of the Ukrainian Army’s best units.
One soldier tells us they have an edge because they have heart and soul.
"We know we are fighting for our country. I don’t know who or what they are fightingfor," he says.
At Odesa train station the music put out by the public address system is a soulful lament.
How fitting. The Russians are coming.
Women and children for the most part hope to catch the midnight train to somewhere safe, but many will be disappointed.
The soldiers ask for people from the battleground town of Mykolaiv to put their hands up.
This is their train and people from elsewhere will have to wait for another.
Everyone who boards the train is frightened and exhausted. Looking in from outside the carriage windows are like frames around pictures of sadness and separation.
All the women and children have said goodbye to their menfolk. They have made their pledges to meet again, don’t know where, don’t know when.
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