Alieu Kosiah, 45, who was arrested in Switzerland in 2014, is accused of murder, rape and a string of other crimes committed in the first of Liberia's back-to-back civil wars, which together killed some 250,000 people between 1989 and 2003.
No Liberian has ever been convicted — either in the west African country or anywhere else — of war crimes committed during the conflict.
The trial is being held at Switzerland's Federal Criminal Court in the southern city of Bellinzona.
At the start of proceedings, Kosiah told the judge Jean-Luc Bacher that he had been held in prison “for six years and one month,” the Swiss news agency ATS reported, adding that he was being held in a jail in the capital Bern. He denies all the charges.
Kosiah was accompanied in court by his duty lawyer, Dimitri Gianoli. The trial has been repeatedly postponed due to the coronavirus crisis.
But even as Switzerland remains hard-hit by a second wave of Covid-19 infections, the judiciary finally managed to set dates for the initial part of the hearing, which is due to last until December 11.
Call for postponement
Kosiah's alleged victims will not be able to come from Africa to testify until next year.
Lawyer Alain Werner, representing four of the alleged victims, called for the trial to be postponed so that they could be present, or, at least, for the hearings to be live streamed to Liberia.
Switzerland recognises the principle of universal justice, allowing it to try people suspected of committing the most heinous international crimes regardless of where they were committed.
But this is the first time its civilian court system has heard an international war crimes case.
Kosiah is the first Liberian to face trial over alleged war crimes committed during its first civil war, from 1989 to 1996, according to Human Rights Watch (HRW).
Liberia's former warlord-turned-president Charles Taylor was convicted in 2012 of war crimes and crimes against humanity — but that was over atrocities committed in neighbouring Sierra Leone, not in his own country.
The Swiss prosecution accuses Kosiah of a string of war crimes while he served as a commander of the United Liberation Movement of Liberia for Democracy (ULIMO) — an armed group created to fight Taylor's rebel force.
Among the charges is the recruitment of children as fighters, pillaging, ordering killings and committing murder himself.
Cruel treatment of civilians, the desecration of corpses and rape are also among the accusations.
Wars still resonate
Liberia's two civil wars were marked by numerous massacres committed by often drugged-up fighters, mutilations, and sexual violence used as a weapon of war.
The widespread use of child soldiers and even cannibalism were also among the horrors seen during this period. Most of the commanders of the different groups fled the country after the wars ended in 2003 and, like Kosiah, a number of other suspected Liberian war criminals have been arrested abroad.
But more than 15 years after Liberians laid down their arms, many of those in charge back then still hold positions of political and economic influence in the country.
And many of the recommendations put forth in a 2009 Truth and Reconciliation Commission report have remained unimplemented.
The underlying causes of the conflict — including ethnic divisions and economic disparities — remain strongly felt in Liberian society.