Former Liberian leader Charles Taylor has been found guilty of war crimes after a five year trial.
Taylor, 64, described by prosecutors as an "intelligent, charismatic manipulator", was in the Dutch court to hear the verdict.
He was found guilty of aiding and abetting 11 charges of war crimes and crimes against humanity at the Special Court for Sierra Leone in The Hague.
The offences included acts of terrorism, murder, rape, sexual slavery, the use of child soldiers and outrages of personal dignity.
Taylor was found to have built a rebel army which used terror tactics to slaughter and mutilate thousands during Sierra Leone's 11-year civil war.
The Revolutionary United Front (RUF) carved its name in the backs of more than 1,000 children to stop them escaping and amputated the limbs of their victims.
Taylor was found to be criminally responsible for providing guns to the RUF in return for blood diamonds while he was leader of Liberia.
The RUF was infamous for using child soldiers, who were often drugged on cocaine and gunpowder when they carried out their killings. The RUF was also known for brutally amputating its victims' limbs with machetes, with up to 20,000 victims reported.
But he was cleared of ordering the atrocities carried out by the RUF directly.
The three judges at the court said that despite his "substantial influence" over the rebels he did not have effective control of their activity.
"The chamber finds beyond reasonable doubt that the accused is criminally responsible... for aiding and abetting the commission of the crimes," said the presiding judge Richard Lussick.
Lussick added: "People were beheaded and their heads displayed at checkpoints ... one civilian was killed in view of the public, disembowelled and his intestines stretched across the road to make a checkpoint."
Taylor was indicted by a United Nations Special Court in 2003 on charges of murder, rape and sexual slavery.
After the indictment Taylor fled into Nigeria, but was arrested in 2006 after attempting to cross the border into Cameroon, and forced to face the Special Court for Sierra Leone.
His trial at The Hague began in 2007 but quickly descended into chaos after Taylor fired his lawyer and attempted to boycott proceedings.
The trial resumed in 2008, and hit the headlines again in 2010 when supermodel Naomi Campbell and actress Mia Farrow gave evidence.
The prosecution has attempted to prove Taylor used 'blood diamonds' to pay for the RUF by linking uncut stones he gave Campbell in 1997.
During Taylor's seven month evidence to the trial he denied allegations of cannibalism in response to claims he had eaten human liver. Judges also heard witnesses who said the RUF fighters ate human flesh and flung the intestines of the people they murdered in the road.
Taylor is the first former head of state to be convicted of war crimes by an international court since the Nuremberg trials after the Second World War.
It is likely he will now be imprisoned in the UK, after the Netherlands agreed to host the trial only if he served his term abroad.
He will be back in court on 16 May, when Taylor will have a chance to make a 30-minute statement. The sentence itself will be handed down on 30 May.
Elise Keppler, senior counsel for Human Rights Watch, said in a statement that the conviction was a "victory" for the victims: "Taylor's conviction sends a powerful message that even those in the highest level positions can be held to account for grave crimes.
"Not since Nuremberg has an international or hybrid war crimes court issued a judgment against a current or former head of state. This is a victory for Sierra Leonean victims, and all those seeking justice when the worst abuses are committed."
More than 120,000 people died in the Sierra Leone conflict between 1991 and 2002.