Following the start of the Sierra Leone Civil War in 1991, Koroma commanded government forces against the Revolutionary United Front (RUF) rebel group.

The following year, he was freed from prison following a coup overthrowing Kabbah, and became the leader of the Armed Forces Revolutionary Council (AFRC) military junta.

Koroma allied himself with the RUF and presided over mass looting, murder and rape against civilians, aid workers, and peacekeepers over his roughly nine months in power.

Koroma was born to Limba parents in Tombodu, in the Kono District of eastern British Sierra Leone, and grew up in Freetown, the capital.

He commanded government forces who were fighting against the Revolutionary United Front (RUF), a rebel army led by the warlord Foday Sankoh.

Koroma cited corruption, erosion of state sovereignty, over-dependence on foreign nations, and leaders' failure to address tensions between the SLA and government-backed tribal militia movements (in particular the Kamajors) as the pretext for the coup.

Koroma's story was consistent with that of the AFRC, which cited the failure of the Abidjan Peace Accord struck between the government of Sierra Leone and the RUF on 30 November 1996.

By 2 June 1997, the RUF/AFRC found itself at odds with Nigerian forces, which were deployed unilaterally under the Economic Community of West African States' Ceasefire Monitoring Group (ECOMOG) and its mandate of August 1997.

Koroma immediately sought to ease the situation, seeking mediation, which resulted in the signing of a peace accord in late October 1997 in Conakry, Guinea.

On 1 March, ECOMOG forces commenced operations in provincial Sierra Leone, removing the RUF/AFRC from every key town except Kailahun (in the far east of the country).

The leadership of the RUF oversaw negotiations with the government of Sierra Leone that led to the signing of the Lomé Peace Accord on 7 July 1999.

According to the indictment, the RUF/AFRC, under the orders of Koroma, had led armed attacks in Sierra Leone in which the primary targets included civilians, humanitarian aid workers, and UN peacekeeping forces.