The ruined seaside city of Mariupol, whose capture has become a key Russian objective, is now irrevocably etched into Ukrainian history, regardless of the outcome of the war.

In the end, a small group of outgunned and outmanned nationalist fighters held out for months, drawing Russian airstrikes, artillery and tank fire down upon the massive Azovstal steel plant, where they made their last stand.

“The 83 days of the defence of Mariupol will go down in history as Thermopylae of the 21st century,” said Mykhailo Podolyak, an adviser to Ukraine’s president.

“The Azovstal defenders thwarted the enemy’s plans to seize eastern Ukraine, drew away enormous numbers of enemy forces, and changed the course of the war.”

Thermopylae is widely considered one of history’s most glorious defeats, in which 300 Spartans held off a much larger Persian force in 480 BC, before finally succumbing.

They were killed to a man, including their king.

Mariupol’s martyrdom first came into focus with the March 9 Russian airstrike on a maternity hospital, then with another airstrike a week later on a theatre that was serving as the city’s largest bomb shelter, with the word CHILDREN written in Russian on the pavement outside to deter an attack.

Nearly 600 people were killed, inside and outside the theatre, by some estimates.

Suddenly, no place felt safe, and its residents fled by the thousands.

But those at Azovstal, the steel mill in the port on the Sea of Azov, hunkered down in the labyrinth of tunnels and underground rooms.

On some days, it was targeted by dozens of explosions. Little by little, the Azovstal civilians took advantage of humanitarian ceasefires to flee.

Finally, on Monday, more than 260 fighters, some of them seriously wounded and taken out on stretchers, emerged and turned themselves over to the Russian side.

The two governments are negotiating their fate.

Other fighters, their precise numbers unknown, remain inside the ruins that sprawl over four square miles in the otherwise now Russian-held city of shattered buildings and apartment blocks.

What Russia described as a mass surrender, the Ukrainians say was a mission fulfilled.

The capture of the strategic port city would allow Moscow to link the Crimean Peninsula, which it annexed in 2014, with the separatist regions of the Donbas that it now controls, and on to the Russian border.

Seizing Mariupol also gives Russian president Vladimir Putin an elusive military victory – won at the cost of the city itself, which lies in ruins as it has since the siege began at the beginning of March.

One Mariupol resident, who fled her home in April with little hope of return, said: “It is very difficult when you see that your city, which has been built before your eyes and restored, becoming more and more beautiful, is dying.”