The child army, which has beaten back well-equipped regular troops and terrorised the population since the mid-1990s, has grown up and thrived.
Drug abuse has been a key factor in the shocking fanaticism of Mr Sankoh's Revolutionary United Front (RUF).
Former child soldiers say they were forcibly injected with cocaine before being sent into battle.
They have gone on to kill, abduct, rape and maim thousands of their fellow countrymen, famously imposing their reign of terror by hacking off the limbs of victims, including children and infants, with machetes.
Youth power
The RUF has no identifiable ideology, but can be defined by opposition to the corrupt political elite in Freetown which has plundered the nation's mineral wealth.
Many foot soldiers were conscripted through kidnapping or the temptation of winning power and status by wielding a gun.
Its roots go back to 1991, when Mr Sankoh, a former army corporal, formed an alliance with a Liberian militia, the National Patriotic Front for Liberia, led by Charles Taylor, who went on to become President of Liberia.
Far from being a puppet offshoot of the Liberian factions, the RUF took on a life of its own and fought successive Sierra Leonean governments.
In May 1997, the RUF joined forces with a group of junior army soldiers, to overthrow the elected government of President Ahmad Tejan Kabbah.
Their youthful brutality and swaggering self-confidence, with matted locks and tattered clothes, inspired terror in the adult population.
Discipline
Appearances belie their tight discipline and fierce loyalty to commanders.
They travel light, care little for their personal safety, and are at home in the thick forest that comes to the very edge of the city.
The junta which the RUF supported was ousted by the West African intervention force, Ecomog, in February 1998, but the rebel soldiers returned a year later to inflict more horrific punishment on the inhabitants of the capital Freetown.
In the subsequent peace process, which gave the RUF a share in government, there were allegations that rebels were continuing their familiar tactics of deliberate mutilation, rape, sexual slavery and murder.