Alieu Kosiah was a commander of a Mandingo-based faction of the United Liberation Movement of Liberia for Democracy (ULIMO) between 1993 and 1995 in Liberia. ULIMO, which entered Western Liberia in 1991, fought against the National Patriotic Front lead by Charles Taylor during the first Liberian civil war. The group managed to gain control over several areas of the region, including Lofa county.
While Kosiah served as commander, mass atrocities were committed by ULIMO fighters. Reportedly, Kosiah directed and participated in the commission of systematic killings, rapes and forced labour of civilians in the Lofa county.
At the end of the Liberian civil war in 1997, Kosiah moved to Switzerland, where he obtained permanent resident status.
In 2014, a group of seven people living in Liberia alerted the Swiss Prosecutor of Kosiah’s alleged crimes, and filed a complaint against him. In August 2014, the Swiss Prosecution decided to open an investigation against Kosiah.