The Ukrainian city of Mariupol has been decimated by Russian shelling, with the true extent of the damage still unclear.
The situation on the ground remains volatile and civilians are still trapped, with disagreements over humanitarian corridors leaving people in hiding with almost no access to food, fresh water and electricity.
Russia said it would allow civilians to escape Mariupol through humanitarian corridors if Ukrainian troops surrendered — Ukraine refused to disarm.
Here's what we know about why Russia sees Mariupol as such an important target, and what it could mean for the region and its people more broadly.
It's a crucial geographic gain for Russia
Mariupol is one of Ukraine's closest cities to the Russian border and is a crucial port linking Ukraine to the Black Sea.
Professor of Peace and Conflict Studies at UQ, Alex Bellamy, says Mariupol is currently between groups of Russian troops advancing from multiple directions.
"Russia's strategic goal appears to be to link up its forces moving north and east from Crimea with those moving west from Donbas and create a single Russian-controlled territory along Ukraine’s south-eastern coast," he says.
The University of Sydney's Professor Emeritus Graeme Gill, an expert in Russian politics, says Mariupol is also in the path of a more easily accessible land corridor from Russia to Crimea, which can be difficult to get to.
"If such a corridor were established and retained, it would greatly improve Russian access to Crimea, which at the moment is limited to one land bridge and by sea," he says.
Graphics from the US Institute for the Study of War, dated 3pm ET on March 21 (6am March 22 AEDT) indicate that Russia has military personnel around most of Mariupol's north-east and south-west, leaving Mariupol almost surrounded:
The Ukrainian Azov Brigade has links there
The Azov Regiment is a military unit that was absorbed into the Ukrainian National Guard in 2014, with some personnel based in Mariupol.
The far-right unit is only a very small part of Ukraine's defence force, but Russia — particularly Russian media — has played up its influence.
The BBC's security correspondent Frank Gardner says because of Mariupol's links to the military group, it gives Russia an opportunity to use the concept of ridding Ukraine of Nazis as justification for its invasion.
"Although they form only the tiniest fraction of Ukraine's fighting forces, this has been a useful propaganda tool for Moscow, giving it a pretext for telling Russia's population that the young men it has sent to fight in Ukraine are there to rid their neighbour of neo-Nazis," Mr Gardner explained in the UK publication.
"If Russia manages to capture alive significant numbers of Azov Brigade fighters it is likely they will be paraded on Russian state-controlled media as part of the ongoing information war to discredit Ukraine and its government."
Putin doesn't like being told 'no'
On the weekend, Russia gave Ukraine an ultimatum: surrender Mariupol, and it would offer safe humanitarian corridors to evacuate all the civilians left in the city.
The offer was almost immediately rejected.
Ukraine's President Volodymyr Zelenskyy's government responded that it would never bow to ultimatums and Deputy Prime Minister Iryna Vereshchuk told the Ukrainska Pravda news portal there was "no question of any surrender".
Professor Gill says it's doubtful Russian President Vladimir Putin would have been surprised by Ukraine's resistance to surrender Mariupol, but is also unlikely to change his stance on the invasion.
There have been multiple reports of Russia disregarding agreed-upon humanitarian corridors since the invasion began.
Citizens are being worn down
Ukrainian authorities say shelling in Mariupol has increased in the past few days — an art school and a theatre both acting as civilian shelters have been bombed, with an unknown number of casualties trapped under rubble.
There are reports that between 40,000 and 100,000 people have fled the city since the invasion began, but exact figures on how many people got out and how many people haven't aren't clear.
Access to food, water and electricity has been widely cut off and communications are limited.
"It seems clear that the Russians are systematically targeting the city’s military and civilian infrastructure with the aim of terrorising the population into submission by creating fear and depriving soldiers and civilians alike of the essential necessities to sustain life," Professor Bellamy says.
"The effects of this war will endure in Ukraine long into the future. Whatever normalcy comes to mean, it won’t be the same normalcy that existed prior to this war, or that of 2014.
"The Ukraine that emerges from the ashes of Russian aggression will be very different, and the challenges will be immense. The West must be prepared to stand with Ukraine, and to support the government and its people, long into the future."
Russia isn't likely to give up until it gets what it wants
Professor Bellamy says Russia is likely to bombard Mariupol until it can take control — destroying whatever it has to in the process.
"The immediate operational goal is to connect the two Russian-controlled areas and to eliminate a pocket of Ukrainian resistance between them," he says.
Professor Gill says the medium to long-term future of the heavily damaged city is yet to be determined.
"If they (Russia) can create a land corridor under their control, it would be in their interests to have a functioning and vibrant city there," he says.
"But it is not clear that, in the short term at least, they will be able to accomplish that."
Professor Bellamy says it's crucial that the West maintains pressure on Russia to withdraw from Mariupol and other Ukrainian cities as the situation deteriorates.
"What we are seeing in Mariupol are classic Russian tactics for urban warfare," he says.
"Sadly, we can expect to see a steady escalation of Russia’s indiscriminate bombardment and the civilian death toll over the coming days unless something is done to stop it."
ABC/wires
