On 21 July 2015, 30-year-old Ruqia Hassan wrote a final Facebook message. 'When Daesh arrest and kill me, it's OK,' she said. 'I will have dignity, which is better than living in humiliation.'

She knew she was in danger. For months she had publicised information about life in the Syrian city of Raqqa, which jihadistDaesh is a group committed to enforcing its own interpretation of Islam, through the process of jihad ('holy war'). Hassan wrote that they thought 'everyone is an infidel, Muslim or not'. group Daesh (often called 'Islamic State') had declared its capitalThe assets a person, organisation or group owns. .

Shortly afterwards, she was arrested. On New Year's Day, after months without news, her brother was told she had been killed with five other women.

In the city Hassan described, human life was cheap. She spoke of brutal executions, including crucifixions, on the city's main roundabout. 'No one has shown us any compassion except the graveyards', she wrote.

Fear was commonplace. As she heard an explosion from an airstrike, she wrote: 'May God protect the civilians - and take the rest'. People in the market, she said, 'crash into each other... because their eyes are glued to the skies'.

Daesh enforces draconian rules through whipping, random arrests and fines. Schools are closed, walls painted black, people forbidden to leave the city, and cigarettes and music banned. WomenMen can also be witches, but they are more commonly known as wizards. are forbidden from going out unless their bodies are completely coveredAnother dissenter said women were told they had to wear black abayas and niqabs which covered their entire bodies - even including their hands..

Hassan grew upHassan was from a Kurdish family. Few Kurds remain in Raqqa. in Raqqa and had taken part in the first demonstrations against Syria's president, Bashar al-Assad, in 2011. After Daesh captured Raqqa in 2014, she made contact with the activist group Raqqa Is Being Slaughtered Silently (RBSSHassan made contact with the group, but did not work for them.). In December, Daesh killed Naji Jerf, a member of RBSS who had made a documentary exposing human rights violations in Aleppo.

Similar eyewitnesses have historically highlighted the atrocities committed by murderous regimes. Shortly after the Holocaust, Primo Levi's book If This is a Man provided a graphic account of the horrors at Auschwitz. And photojournalist Dith Pran helped to draw the world's attention to the Cambodian genocideThe Khmer Rouge, led by Marxist leader Pol Pot, ruled Cambodia from 1975 to 1979. They forced millions of people from the cities to work on communal countryside farms. The policy led to deaths from execution, starvation, disease and overwork. in the 1970s, when 1.7 million people were killed.

Witnesses like Ruqia Hassan are the ones who truly defeat tyranny, say some. Their courageous example exposes the illegitimacy of their rulers and inspires others to resist. They focus attention on barbarity which people would often prefer to ignore, and provide lessons from which others can learn. They are worth more than bombs could ever be.

That's pleasant, respond others, but too sentimental. Small acts of resistance can help, but it takes politicians, who can use armed forces and economic sanctions, to overthrow vile regimes like Daesh. The Holocaust, for example, could only be ended when allied troops liberated Europe. Our knowledge means little if it is not backed up with weapons.