Since war crimes are often committed in a system of armed forces, international law recognises that command hierarchies enable such violations, Robert Heinsch, director of the Kalshoven-Gieskes Forum on International Humanitarian Law at Leiden University, tells DW.

"People who have given orders to normal soldiers or whoever is in charge of launching the attacks can be indicted because of this act of ordering – or even if the person didn't order it themselves, but they were aware or should have been aware of these attacks," says Heinsch. "Because of their function as a military commander, they can be held responsible – and that's very important. This is also incorporated into the German code of crimes against international law, because you would otherwise not be able to hold these people responsible."

In Germany, the law establishing universal jurisdiction has only been used once to convict a perpetrator. In 2015, German judges found Rwandan Hutu rebel leader Ignace Murwanashyaka and his aide guilty of war crimes and crimes against humanity. Murwanashyaka's conviction was overturned three years later and he died while awaiting re-trial.

The only other trial that has employed universal jurisdiction to prosecute perpetrators is the case in Koblenz targeting senior Syrian regime figures for alleged torture.

Just the beginning

In his capacity as Syria's president, Assad heads Syria's armed forces. On several occasions, he has made clear that as commander-in-chief, ultimate authority lies within his office, telling Chinese state broadcaster CCTV in September 2013 that he is "the lead decision-maker in moving and leading the armed forces in Syria."

But other factors are also crucial for a viable prosecution. Even if federal prosecutors decide to cross that threshold and indict the highest regime figures allegedly involved in the decision-making process, other issues could derail the case, including sovereign immunity, under which an acting head of state is traditionally protected from prosecution.

For those pursuing justice against Syria's top regime figures, the endeavour is shy of a Sisyphean task. But that has yet to dissuade them. "We know this process will take 10, 20, maybe even 30 years. So, we must also try to prepare ourselves for a long-term strategy. We know from all of our experiences that this is not something that will be finished within a day," says Mazen Darwish, president of the Syrian Centre for Media and Freedom of Expression. "Maybe it's only the beginning."

Since 2011, Germany's war crimes unit has tasked more than a dozen prosecutors with a structural investigation of war crimes and crimes against humanity in Syria. Germany is now home to an estimated 600,000 Syrians, the vast majority of whom fled their country to escape the brutal conflict. Throughout their asylum applications, they are frequently questioned about their part in atrocities, whether as victims or perpetrators.

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