The future is uncertain for hundreds of Ukrainian soldiers who late on Monday night left the Azovstal steel plant in Mariupol, more than 50 of them seriously injured. They were taken to a Russian detention center at a village near Donetsk.

Ukraine needs its heroes alive, says Ukrainian President Volodymyr Zelensky — he wants them released in a prisoner exchange.

However, an agreement seems far off. Vyacheslav Volodin, speaker of the State Duma lower house of the Russian parliament, has spoken out against a general exchange but said that Russia is doing everything it can to provide medical care and humane treatment for the Ukrainian prisoners.

POW is clearly defined

Should there be an prisoner swap after all, it would not be the first exchange since Russia's invasion of Ukraine. In March, 10 Russian soldiers were exchanged for 10 Ukrainian soldiers, and 41 Ukrainians were released in early May, according to Russian figures. Since the start of the war in eastern Ukraine in 2014, hundreds of prisoners have been exchanged between the Ukrainian government and the pro-Russian separatist areas. Vladimir Putin at the time spoke of "a good step forward, toward normalization."

The question of how to deal with soldiers in captivity has been an issue for centuries. The Geneva Conventions, which are a part of international humanitarian law, detail the concept of prisoners of war — the first convention was drawn up in 1864, and another was adopted in 1929. In 1949, both conventions were revised, also against the background of the atrocities of the Second World War. They are still valid today, and state that inhumane and degrading treatment is illegal.

But what exactly are prisoners of war?

To be considered a prisoner of war, the person in question must have taken part in a conflict or be a member of a military command structure — that is the theory. In practice, this definition does not always apply.

For instance, a 2017 exchange between Ukraine and pro-Russian rebels in separatist-controlled areas in the east of the country included a blogger from Luhansk and two soccer fans from the Sorja Luhansk club. The latter were jailed for burning a Russian flag, and separatists convicted the blogger of treason.

Equal numbers?

Usually, such an exchange is a one-for-one swap, for instance two soldiers for two soldiers. However, there are exceptions. In the 2017 exchange, Kyiv and the rebels, mediated by Orthodox clerics from Ukraine and Russia, agreed to exchange 306 pro-Russian separatists for 74 Ukrainian soldiers and civilians. On the day of the swap, significantly fewer sat on the bus headed to the rebel region, perhaps because some had served their prison sentences or no longer wanted to go there.

In a 2014 example from Afghanistan, US Sergeant Bowe Bergdahl was exchanged after five years of captivity and five high-ranking Guantanamo detainees were put under house arrest in Qatar in return. The case was a disaster for the Obama administration, with critics complaining the price for Bergdahl's release was too high.

When is it time to swap?

Despite numerous examples, the number of overall exchanges has become "more rare during conflict," Paul J. Springer, a US author, professor and military historian told Time magazine in an interview last month. "More and more prisoners tend to be held until the end of the fighting. There are often wartime swaps of sick and wounded prisoners, where there's no possibility they're going to go back into conflict," he said.

During the Korean War, many wounded and sick prisoners were swapped for humanitarian reasons, Springer said, adding they were by then so gravely ill they were to "die at home rather than die in a prison camp."

Regarding the exchange under discussion in Ukraine, 53 soldiers are thought to be seriously injured, a fact that may play a role should it come to a swap after all. 

This article has been translated from German.