On 25 May 1997 Major Johnny Paul Koroma's Armed Forces Revolutionary Council (AFRC) overthrew the elected President Ahmad Tejan Kabbah and allied with the Revolutionary United Front (RUF) of Foday Sankoh. Kabbah went into exile in Conakry. The Abacha regime — already commanding ECOMOG in Liberia — committed Nigerian forces under Lt-Gen. Victor Malu to restore him.
The Nigerian Defence HQ Operation Sandstorm, launched 6 February 1998 from Lungi airport (held by ECOMOG since June 1997 under Brig. Maxwell Khobe), retook Freetown in nine days. Kabbah was restored on 10 March 1998. Nigerian troop strength peaked at 13,000 — again over 80 % of the ECOMOG force. The 6 January 1999 RUF/AFRC 'Operation No Living Thing' incursion into Freetown killed an estimated 6,000 civilians and resulted in heavy ECOMOG casualties; the Nigerian Army's 78 Battalion was effectively destroyed in the fighting around State House and Wilberforce Barracks.
The July 1999 Lomé Accord and the deployment of UNAMSIL in October 1999 enabled the Nigerian withdrawal completed in February 2000 — though approximately 3,000 Nigerian troops re-hatted as UNAMSIL contingents and remained. Total Nigerian KIA in the Sierra Leone theatre exceeded 800 (Adebajo & Keen 2007). The fiscal cost is included in the ECOMOG aggregate of US$8–12 billion. Brigadier Maxwell Khobe, the Nigerian Chief of Defence Staff of the restored Sierra Leone Army (1998–2000), died in office in April 2000 — Sierra Leone declared three days of national mourning. See Sierra Leone relations.