After a 13-years-long investigation, two oil executives eventually went Tuesday on trial in Stockholm, Sweden, for abetting grave war crimes committed more than 20 years ago when a consortium led by their company searched for oil in South Sudan.

In a rare case for a Western company, two top executives from Lundin Energy of Sweden were indicted on Thursday for complicity in grave war crimes committed in Sudan between 1999 and 2003, when the Sudanese army allegedly indiscriminately killed civilians to pave way for Lundin’s oil exploration, prosecutors argue.