“You have to work harder, the graves are not full,” urged the voice on the radio. In April 1994, when the genocide started in Rwanda, ordinary people were glued to their receivers. In a part of the world where most people do not have electricity, that’s the way information gets disseminated. But in Rwanda that spring the popular radio stations seemed to have only one aim: to incite the Hutu masses to exterminate their Tutsi neighbors.

The most popular station of all was RTLM (Radio Televison des Milles Collines), the Thousand Hills Radio Television. It was known for having the best disc jockeys in Rwanda and for its attractive mix of African music, news programming, and political analysis. Founded in 1993 and owned by family members and friends of President Habyarimana, the station preached an extremist message of Hutu supremacy, but many apolitical Rwandans became listeners because of the music it played. In fact, their hearts and minds were being prepared for genocide. When the killing was unleashed on April 6, it became clear what the owners and managers of the station had created—an infernal pulpit from which the message to kill could be disseminated throughout Rwanda.

The incident that triggered the mayhem was the downing of Habyarimana’s plane by a missile. Within minutes of the crash, RTLM journalists accused Belgian troops in Rwanda on a UN peacekeeping mission of shooting down the plane. The next morning, ten Belgian soldiers were brutally killed, and UN forces withdrew. It was RTLM that gave the signal to begin the massacre of Tutsis and moderate Hutus.

RTLM on April 7 and April 8: “You have to kill [the Tutsis], they are cockroaches…” May 13: “All those who are listening to us, arise so that we can all fight for our Rwanda… Fight with the weapons you have at your disposal, those of you who have arrows, with arrows, those of you who have spears with spears… Take your traditional tools… We must all fight [the Tutsis]; we must finish with them, exterminate them, sweep them from the whole country… There must be no refuge for them, none at all.” And on July 2: “I do not know whether God will help us exterminate [the Tutsis] …but we must rise up to exterminate this race of bad people… They must be exterminated because there is no other way.”

The message worked. By July of 1994, when the victory of the Tutsi-led Rwandan Patriotic Front (RPF) put an end to the genocide, up to 1 million Rwandans—mostly Tutsis, but also Hutus belonging to the democratic parties in Rwanda—had been slaughtered. The radios had been all too successful in inciting the genocide.

What they did, which was both to prepare the ground for the killing and encourage listeners to go on killing once the genocide had begun, was, of course, utterly illegal under international humanitarian law, which does not recognize an absolute right to free expression. By definition, most of those killed were civilians, that is, “persons taking no active part in the hostilities.” In an internal conflict, as stated in Article 3 common to the four Geneva Conventions of 1949, civilians “shall in all circumstances be treated humanely without any adverse distinction founded on race, color, religion, sex, birth, or wealth.”

As the rampage spread, the key document became the Genocide Convention of 1948, to which Rwanda became a party in 1975. The convention defines the crime of genocide as “acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group as such.” The acts include killing members of the group, causing serious bodily or mental harm, and deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part. The convention not only makes genocide itself an international crime but states in Article 3 that “direct and public incitement to commit genocide” is punishable. And in September 1998, an ad hoc International Criminal Tribunal for Rwanda (the ICTR), sitting in Arusha, Tanzania, sentenced Jean Kambanda, the former prime minister, for direct and public incitement to commit genocide, in part for encouraging RTLM to continue its calls to massacre the Tutsis. That same month, the court convicted Jean-Paul Akayesu, the leading civilian in Taba commune, on charges that included the direct and public incitement to commit genocide.

The prohibitions set forward by the Genocide Convention and the precedent set by the ICTR were affirmed in the statute of the International Criminal Court (ICC), which was adopted on July 17, 1998. One hundred and twenty nations approved the Rome Statute, which laid the ground rules for the first international criminal court in history; Article 5 of the statute listed genocide first among the crimes over which the court had jurisdiction.

The hate-mongering journalists of RTLM stayed on the air until the very last moment of the Rwandan genocide. In July 1994, when the RPF—the Tutsi army that came from neighboring Uganda—defeated the Rwandan army and put an end to the genocide, the RTLM staff took a mobile transmitter and fled to Zaire, together with Hutu refugees. Ferdinand Nahimana, a well-known historian who served as RTLM’s director, fled to Cameroon. There he was arrested and delivered to the Arusha tribunal, where he will have to answer to a very special charge: incitement to genocide.

The new Tutsi-led government closed RTLM, but the message continued when Hutus launched another clandestine radio station in Kivu, Zaire, to incite hatred against Tutsis in Burundi, using the same slogans.