A former corporal in the Sierra Leonean army, wedding photographer, and television cameraman, Sankoh became a student activist in the 1970s. After his activism earned him a short prison term, Sankoh joined a Cold War guerilla camp in Libya sponsored by Moammar Gadhafi, where Moammar Gadhafi was preaching revolutionary ideas to West African dissidents. It is here that he met Charles Taylor, future president of Liberia and Sankoh's financial benefactor and ally throughout the civil war. With his encouragement, Sankoh and two allies, Abu Kanu and Rashid Mansaray, returned from Libya to form the RUF and begin an insurrection.
His RUF became notorious for brutal practices such as mass rapes and amputations during the civil war. Sankoh personally ordered many operations, including one called "Operation Pay Yourself" that encouraged troops to loot anything they could find. After complaining about such tactics, Kanu and Mansaray were summarily executed. During the ten-year war, Sankoh broke several promises to stop fighting, eventually leading British and Guinean forces to intervene in Sierra Leone with their own small, but professional, military forces. The RUF was crushed. Sankoh was later captured after his soldiers gunned down a number of protesters outside his Freetown home in 2000. His arrest led to massive celebrations in Freetown. Sankoh was handed to the British and, under jurisdiction of a UN-backed court, he was indicted on 17 counts for various war crimes, including crimes against humanity, rape, sexual slavery and extermination.
Sankoh died of complications from a stroke while awaiting trial. The chief prosecutor for the trial said Sankoh's death granted him "a peaceful end that he denied to so many others".