In 1999, slavery was eliminated from Sudan by the stroke of a pen. For five years, UN Special Rapporteur Gáspár Bíró had chronicled the recrudescence of government-sponsored slave raiding in the North-South war, the longest in Africa’s history. The response of the UN Human Rights Commission, at the request of the government of Sudan, was to replace all references to “slavery” in UN documents with the term “abduction.”

For Aweng Deng Nyal, seized in a militia raid in 1991, the news that the slaves of Sudan had been emancipated would have come as a surprise. That is, if she ever heard it. Driven by famine, Aweng had sought food from a southern garrison town. As part of a government strategy to depopulate Dinka areas on the frontline of the war—“to break the backbone of the rebellion,” in the words of the Sudanese Defense Minister Ibrahim Suleiman Hassan—a group of government-backed Arab murahileen horsemen intercepted Aweng, shot her husband, cut her brother’s throat, bound her hands, and dragged her north. For nine months, Yah’ia Muhammed—the man whom she had watched kill her family—forced Aweng to farm his land. She slept fenced in with cattle and, once a day, was given a cupful of boiled sorghum to eat.

In the course of the civil war, Murahileen militias captured over ten thousand Southern Sudanese like Aweng. Most became textbook slaves, raped and forced by violence to work for no pay. A survey by the Rift Valley Institute in 2002 established the identities of over 10,000 southerners abducted in this way.

That enslavement is a crime against humanity is axiomatic. Along with piracy, genocide and torture, it is a crime of universal jurisdiction. Today there are more slaves in the world than at any point in human history. But “slavery” is a word that blurs at the edges, into indentured labor, debt bondage and human trafficking. Large numbers are held in debt bondage on the Indian subcontinent. Millions are forced into prostitution or agricultural work. Are they slaves? In terms of ethics, yes. In international law, not necessarily.

The Slavery Convention of 1926 defines slavery as “the status or condition of a person over whom any or all of the powers attaching to the right of ownership are exercised.” It defines the slave trade as including “all acts involved in the capture, acquisition or disposal of a person with intent to reduce him to slavery” and “all acts involved in the acquisition of a slave with a view to selling or exchanging him.” A Supplementary Convention adopted in 1956 addresses debt bondage and serfdom, which it characterizes as “institutions and practices similar to slavery.” Parties to the Conventions are required to prevent and suppress the slave trade and eliminate slavery and similar practices “progressively and as soon as possible.”

Today, as in the past, enslavement and bondage are often forms of commercial exploitation, bred by chaos—as in Bosnia, Kosovo, Transnistria and Nepal. Sometimes, it is a means to terrorize local populations, as when the Lord’s Resistance Army forced children to take up arms in Uganda. The twentieth century saw the rise of a new, focused use of human bondage. Since Armenia in 1915, slavery and forced labor emerged alongside genocide as a method of erasing cultures.

The Nazis used several million Jews as forced laborers in World War II. The Khmer Rouge in Cambodia destroyed urban culture by forcing city dwellers into rural labor camps. In Bosnia Serbian forces established camps where Bosnian Muslim women were forced to have sex with non-Muslim men, with the aim of breeding Muslims out of Bosnia. And in Sudan, as Aweng Deng discovered, successive governments in Khartoum abetted northern Arab militias to revive the practice of slave raiding that the British had stamped out after the reconquest a century earlier.

Slavery is as old as war. Since antiquity slaves have been the spoils of battle. But the nineteenth century saw the crumbling of the ideological justification for the “peculiar institution” as it was known in the United States. The first codification of the laws of war—the Lieber Code promulgated by President Lincoln during the American Civil War—contained a provision against enslavement. The Geneva Conventions of 1949 do not specifically forbid slavery, but its prohibition is implicit in other rules. The second Additional Protocol of 1977 includes a ban on slavery in civil wars. The prohibition of slavery is also regarded as a rule of customary law applicable in all conflicts. The statute of the International Criminal Court lists enslavement and sexual slavery as crimes against humanity.

But the UN’s antislavery efforts have not been robust. Member States demonstrated little appetite for projecting force in order to stop slavery and slave-like practices that occurred during civil wars. And when international criminal courts handed out indictments after wars ended, charges of slavery were few and flimsy.

On March 1, 2006, in his last appearance before the International Criminal Court (ICC), Slobodan Milosevic accused the Kosovo Liberation Army of “white slave trading.” The charge was true and also hypocritical, since it was on Milosevic’s watch that the Serbian army had established the internment camps where the forced labor and killing of Bosnian Muslim men and the mass rape of Bosnian Muslim women took place. But no high Serb official has been convicted of enslavement.

Take the case of Milorad “Mico” Krnojelic, the director of the notorious KP Dom concentration camp in the Bosnian town of Foca. Mico oversaw the illegal imprisonment—and in many cases torture, murder and enslavement—of over 760 Muslim and other non-Serb civilians. Mico’s guards forced dozens to work, under threat of solitary confinement or worse, on the front lines.

The International Criminal Tribunal for the former Yugoslavia (ICTY) charged Mico with enslavement of the prisoners. While Mico was sentenced to fifteen years for murder and torture, and while other Serb officers were convicted of enslavement, prosecutors failed to prove he gave the orders, and he was acquitted of slavery charges.

The international criminal justice system faced another challenge when former Liberian president Charles Taylor was transferred for trial in The Hague. Between 1998 and 1999, rebels sponsored by Taylor brought chaos to neighboring Sierra Leone. Massacres and amputations sparked international outrage, but forced conscription, forced labor and sexual enslavement were equally destructive atrocities. Boys were forced to bear arms. Girls were captives in sex slave camps. In some cases, their ordeals continued for years.

In 2003, Taylor was charged with enslavement and sexual slavery, crimes against humanity under the Statute of the Special Court for Sierra Leone. With his trial due to start shortly, his conviction is far from certain.

Back in Sudan, one day in 1992, Yah’ia Muhammed’s elderly mother, a humane woman who often cried when she saw her son beat the slaves, brought Aweng some water. “My son is going to kill you today,” she said. “He is bringing in fresh slaves who will work harder.”

Aweng ran to a neighboring village. There, when Muhammed’s overseers came looking for her, a free Dinka family hid her under a plastic sheet in their mud and straw tukul. When the war ended eleven years later, she was finally able to return to her smashed home in southern Sudan, where I found her in May 2003. In Sudan, slave-raiding ended with the peace agreement in the North-South war. But thousands of abducted people are still held in bondage. Sudan, like every other country in the world, is a signatory to the international conventions on slavery; and slavery is a crime under Sudanese law. Complicity at the highest levels of the government and the military-security apparatus is clear. But no one in Sudan has ever been charged with enslavement, let alone convicted.

(See sexual violence: enslavement, child soldiers.)