A destroyed armoured vehicle during ongoing conflicts in the city of Mariupol. Photo / Getty Images
"This is not a martyr city. It is a fighter city. And we are not in the past, we are in the present, you understand?"
That was the defiant message issued by Syatoslav Palamar, a captain in Ukraine's Azov regiment, from inside Mariupol on Monday.
"While we are here, Mariupol continues to be Ukrainian," he concluded from an underground bunker.
The imminent fall of Mariupol has been predicted for weeks, and the survival of its defenders is one of the constant surprises of the war.
The situation looked to become all the more drastic on Monday night, as the Azov regiment said in a statement on their Telegram channel that Russian forces appeared to have used chemical weapons. "Russian occupation forces used a poisonous substance of unknown origin against Ukrainian military and civilians in the city of Mariupol, which was dropped from an enemy drone.
"The victims have respiratory failure … the effects of the unknown substance are being clarified."
The claim could not immediately be verified, but it came after Eduard Basurin, a spokesman for the self-proclaimed Donetsk People's Republic, told Russian state television that the Kremlin's forces might resort to chemical weapons to end a conflict that has unexpectedly dragged on for weeks.
Volodymyr Zelenskyy, the Ukrainian president, said Russian forces could use chemical weapons, but he did not say whether any had been used.
Liz Truss, the Foreign Secretary, addressed the claims, saying: "Any use of such weapons would be a callous escalation in this conflict and we will hold Putin and his regime to account."
Tens of thousands of people have been killed in the southern port city, Zelenskyy said on Monday.
And he made clear it could be the most important battle of the war.
"Mariupol is the heart of this war today. It is beating. We're fighting. We're strong. And if it stops beating we will be in a weaker position.
"They are people who are distracting a big part of the enemy forces. The stronger our position in Mariupol, the stronger our position in the east of the country will be. And if they are stronger, the negotiation table will be closer and we will have advantages in the dialogue with the Russian Federation."
If Mariupol falls, and the looming battle for the east goes badly, he warned, Russia would seek to press its advantage and continue the war.
Both sides are aware of the importance of the battle.
"If and when it does fall, then those forces which are engaged there are free to attack north to attempt to join up with those forces that are attacking south from Izyum," said a Western official. "The Ukrainians are now going to face effectively a pincer move."
The official said Russia would be looking to "double or triple" the forces available to it in Donbas before attempting that operation, and that it "is going to take some considerable time to bring them up to that sort of number".
The length of the siege, the scale of the destruction and the bravery of the defenders of Mariupol has drawn inevitable comparisons with Stalingrad.
But Stalingrad famously ended in a seemingly miraculous victory for the defenders. There is a more recent, and bitter, precedent many Ukrainians will have in mind.
In 2014 and 2015, small numbers of Ukrainian troops battled for months to hold onto the wreckage of Donetsk airport against impossible odds. They became a symbol of heroism and defiance, but the fight ended in inevitable and painful defeat.
Will Mariupol end the same way?
The siege began on March 3, when Russian spearheads from Crimea and Donbas met and completed an encirclement of the port city.
Although there are rumours of secret supply routes, reinforcement has been effectively impossible ever since.
The Russians quickly targeted essential utilities including water and electricity to make life impossible for both the defenders and the 400,000 or more civilians trapped in the city.
They also destroyed communications infrastructure, making it nearly impossible to speak to those trapped inside or document the realities of the battle.
For the first three weeks, Mstyslav Chernov and Evgeniy Maloletka, two journalists with the Associated Press, continued to work under shell fire, sending pictures and words when they could still get a tiny bit of signal.
They documented the Russian airstrike that destroyed a maternity hospital, killing at least one heavily pregnant woman and her unborn child, but had to leave when they were warned that the Russians were hunting for them.
Since then, we have had to rely on infrequent updates from the city council and the harrowing testimony of the civilians who very occasionally make it to safety along a "green corridor".
The stories, however, are consistent: no water, no food, no heating, no medicine. Intense fighting, total destruction of neighbourhoods and bodies lying in the street.
Russian infantry and armour backed by the unrestricted use of artillery and airstrikes have moved block to block in a vicious street-to-street, house-to-house fight with a few thousand Ukrainian marines, border guards and Azov regiment fighters.
The footage that has emerged resembles the aftermath of the Second World War. Apartment blocks are blackened shells, smoke rises from across the city, and theatres have been reduced to rubble.
Captain Palamar in his video described a battle of desperate odds, with casualties so high subalterns have found themselves in command of battalions, officers killing themselves with grenades and a constant lack of drinking water.
"Everyone is happy because the horde does not go further, but have you thought about how it is to be here, to fight in such conditions?" He asked.
"It's when they text you – 'How are you, buddy?' – when five minutes ago you put down a black bag with a brother you knew for seven years.
"It's when your friends hide their eyes because they are ashamed to say they are too afraid to come and help you."
Yet the defence has been tenacious and resourceful, making extensive use of ambush and better knowledge of the city.
One video that emerged early on in the battle showed a Ukrainian infantry fighting vehicle dodging down side-streets to ambush Russian tanks.
"The fall of Mariupol has been long predicted by many and the forces there continue to fight extremely bravely, and in the situation they are in, incredibly effectively," a Western official said on Monday.
Nonetheless, the defenders above ground have been pushed back, street by street.
The Ukrainians are now believed to be confined to a number of isolated pockets, the largest of which centres on the Azovstal Iron and Steel works.
On Monday, the Facebook Page of Ukraine's 36th Marines posted a letter saying it was nearly out of ammunition and that it anticipated the "final battle".
"From now on, it is hand to hand combat, then death for some of us and captivity for others," it said in a letter that was markedly more downbeat in tone than Captain Palamar's video.
But like so much in this battle, it was impossible to verify.
Petro Andryushchenko, an aide to the Mariupol mayor, then said on social media that the marines' page had been hacked and the post was fake.
A maze of gantries, chimneys and pipes that covers hundreds of acres, and is bound by the sea to the south and the Kalmius river to the west and north, Azovstal is a formidable citadel.
And even Russian sources appear to acknowledge how effective the Soviet-built factory is as a redoubt.
Eduard Basurin, a spokesman for the self-proclaimed Donetsk People's Republic, told Russian state television on Sunday that Russian forces might resort to chemical weapons to finish the job.
"There are subterranean floors there, therefore to take said object by force makes no sense. Because we could allocate a large number of our soldiers, and the enemy will not suffer such losses," he told Channel 1.
"Therefore at the moment, we need to deal with the blockage of this factory, we need to find exits and entrances, in principle, it can be done. And after that I think we need to turn to chemical forces, which will find a way to smoke moles out of their holes."
As of Monday afternoon, both Western and Ukrainian officials insisted the battle was not over.
The Ukrainians, and particularly Azov's slick media operation, are still posting footage of their successes, to tell the country and the world that they are still fighting.
As recently as Friday, they released footage of a soldier firing an anti-tank missile at an armoured vehicle from the roof of a building.
On Monday, they published fresh footage purporting to show a Ukrainian mortar strike on Russian vehicles in the courtyard of a bombed-out apartment building.
There is no shortage of similar footage claiming success on pro-Russian media, however.
Semyon Pegov, who runs the pro-Russian outlet War Gonzo, posted a video of himself on the waterfront near Mariupol port, the centre of one pocket of resistance.
Smoke and flames could be seen rising in the distance. "The city is burning. Fighting continues," he said.
He claimed the Ukrainians were being pushed to the far corner of the port facility and predicted they would either "surrender, die or try to break out" in "not weeks, really a matter of days."
It is clear the Russians are making progress. But that is a prediction the defenders will seek to once again defy.
The factory had produced 6616 tons of toxic gases by the war's end.