An international criminal tribunal in The Hague has found Charles Taylor guilty of all 11 charges relating to the bloody civil war in Sierra Leone.
The former president of Liberia looked despondent as Judge Richard Lussick listed the charges, which included murder, rape and the conscription of child soldiers - offences that are classed as war crimes as well as crimes against humanity.
Although Taylor did not commit the atrocities himself, the court ruled that there was sufficient evidence to show that he had "aided and abetted" the commission of crimes through his dealings with rebel groups.
In exchange for diamonds ,Charles Taylor had provided weapons, food, fuel and equipment to rebels carrying out atrocities in Sierra Leone.
Our Europe Correspondent Martin Geissler reports from the trial in The Hague, on the message today's verdict sends to other brutal rulers.
Today's hearing brings to an end a lengthy process that began with Taylor's indictment in 2003, while he was still President of Liberia. Soon after, he resigned and went into hiding in Nigeria.
His conviction is the first time a former head of state has been convicted by an international court since the Nuremberg Trials of Nazi leaders in 1946.
The lead prosecutor Brenda Hollis hoped that today's ruling would bring "some measure of justice to the many thousands of victims who paid a terrible price for Taylor's crimes".
The court found that Taylor gave "sustained and significant" support to the Revolutionary United Front (RUF) rebels in Sierra Leone. However, the judge ruled that the evidence fell short of showing that Taylor ordered the crimes.
Taylor's support included selling so-called blood diamonds in exchange for arms and ammunition, which he passed on to the rebels. The judge said that Taylor was aware that the rebel group was responsible for serious crimes.
Earlier in the trial, the supermodel Naomi Campbell was asked to testify about some blood diamonds Taylor gave her at a banquet they both attended in South Africa in 1997.
Taylor's association with such diamonds, which Miss Campbell famously described as "dirty little stones", were key in bringing him to justice.
The civil war in Sierra Leone lasted for a decade and claimed the lives of some 50,000 people. Numerous atrocities occurred including widespread amputations and rapes.
Human rights groups have hailed the conviction as reminder that not even heads of state are immune from prosecution.
Taylor will be remanded in custody until a sentence hearing on 16th May, and the final sentencing on 30th May. He has the option of appealing the judgement before then.
If he receives a prison sentence he will serve it in the UK.