With the evacuation of some civilians from a steel mill besieged by Russian forces in the port of Mariupol, attention is turning to the fate of hundreds of Ukrainian troops still trapped inside the plant’s labyrinth of underground tunnels and bunkers after weeks of siege.

With both able-bodied and wounded members among their ranks, their options appear to be fighting to the death or surrendering in the hope of being spared under international humanitarian law. Experts say the troops are unlikely to be given an easy exit and may struggle to leave as free men or even alive.

According to Laurie Blank, a professor of international humanitarian law and law of armed conflict at Emory Law School in Atlanta, injured fighters are considered “hors de combat” — literally “out of the fight” — and can be detained as prisoners of war.

After a grueling, obliterating siege of Mariupol, the sprawling, seaside Azovstal mill is a key war objective for Russian forces as the last holdout of resistance in coastal southeastern Ukraine.

Kateryna Prokopenko, whose husband, Denys Prokopenko, commands the Azov Regiment at the plant, told The Associated Press that she went more than 36 hours without hearing from him before finally hearing from him on Wednesday.

Ukrainian authorities have also demanded that Russia provide the Azovstal soldiers with a safe way out — armed with their weapons. However, experts say that simply allowing them to walk free would be unprecedented, not least because they could take up arms again, potentially causing Russian casualties.

Instead, the Russian military has ordered all troops within Azovstal to lay down their weapons and raise white flags. According to international law, those who surrender will not be killed.

However, the commanders of the Ukrainian resistance at the plant have repeatedly denied this. Sviatoslav Palamar, the Azov Regiment’s deputy commander, said in one video recording from the plant that his forces were “exhausted,” but that “we have to hold the line.”

Given its alleged previous violations of rules governing war conduct and a lack of evidence for how it has been treating Ukrainian soldiers in custody, it is unclear whether Russia would uphold its commitments under international law regarding POWs if the Azovstal fighters were captured.

POWs are entitled to “absolute protection against ill treatment and murder” under international humanitarian law. Violations of these norms are considered war crimes, according to Annyssa Bellal, senior researcher and international humanitarian law expert at the Geneva Graduate Institute. “However, compliance with the norms is contingent on the willingness of the conflicting parties.”

Both sides are accused of violating international norms during the two and a half months of war, as evidenced by evidence of execution-style killings of civilians following Russian withdrawals near Kyiv and the desecration of corpses that may have been Russian troops outside Kharkiv.

However, there are differences of opinion about whether injured combatants can be targeted in war, according to Sassoli, who was part of a three-person team sent to Ukraine by the Organization for Security and Cooperation in Europe in March.

In conflicts around the world, the International Committee of the Red Cross plays a critical and nearly exclusive role in mediating between combatants on issues such as arranging prisoner swaps and monitoring detainee conditions. The ICRC, among other things, collects names of POWs and reports them to their governments and families.

On Tuesday, Pascal Hundt, the ICRC’s chief in Ukraine, told reporters that a Russian-Ukrainian agreement that resulted in the recent evacuations from Azovstal covered only civilians. And he expressed doubt that anyone else would be able to escape.