In November 2014, a group of Mauritanian activists assembled the Caravan of Liberty, a cross-country convoy that would travel to various villages and educate citizens about slavery and land rights. It was an act of bravery in a country where human rights defenders are routinely imprisoned and police are known to open fire on peaceful demonstrators.

The activists hoped the Caravan would draw attention to a most heinous and widespread human right violation in Mauritania: slavery. In 1981, Mauritania became the last country in the world to abolish slavery, but the government did not criminalize the practice until 2007. Despite these measures, enforcement of anti-slavery laws is nearly non-existent and as a result there are reportedly at least 155,600 slaves in Mauritania, roughly 4% of the population.

Given the Mauritanian government’s hostility to civil society, it should come as no surprise that the Caravan did not last long. Just four days into the trip, the Caravan was met by 600 police officers outside the city of Rosso, attacked with tear gas and sticks, and its leaders promptly arrested.

Ten activists were put on trial, but only three were convicted and received prison sentences. Two of the men, Biram Dah Abeid and Brahim Ramdane of the organization IRA-Mauritania, remain in prison today. Their colleague, Djiby Sow of the organization KAWTAL, was released last summer on medical grounds and is in France receiving treatment. He can be returned to prison if he sets foot in Mauritania.

Since their incarceration, Biram and Brahim have been kept in inhumane prison conditions. They are confined to one windowless cell about 6 square meters, which is filled with vermin. Temperatures regularly rise above 100 degrees Fahrenheit. The prison authorities provide them with neither bedding nor with nourishing food. Biram’s family has relocated to the town near the prison in order to bring them necessary food parcels, sleeping mats and mosquito netting.

In addition to these inhumane conditions, Biram suffers from several serious health issues and prison officials have refused to heed treatment recommendations made by outside physicians or to move him to a hospital.

Today marks one year since the Mauritanian government sentenced these peaceful activists to serve prison sentences for daring to speak out against the deplorable practice of slavery. Despite their imprisonment, they still have hope. In August 2015, Biram wrote a letter to his supporters, emphasizing: “I refuse to give up. I will not be silenced. I will not stop challenging the dogma which is used to legitimize slavery here.”

The detention of these men is not just a violation of international law and basic human rights; it is a troubling sign that the Mauritanian government has no interest in freeing 140,000 of its citizens from bondage. We strongly urge the Mauritanian government to immediately and unconditionally release Biram and Brahim and to ensure that Djiby is not imprisoned when he returns from medical treatment abroad.