As demonstrations spread, so did arrests. Syria already had a well-documented network of prisons where torture and forced confessions were common. But it expanded to what a United Nations Commission of Inquiry and human rights groups have described as an industrial scale, holding tens of thousands at any one time. Thousands have been executed in just one facility, Saydnaya prison, Amnesty International found.
The United Nations commission, in a report last year, quoted a defector from an intelligence agency as saying officers had orders to arrest male demonstrators between the ages of 16 and 40; another defector described his training in techniques that detainees have described, like beatings with cables, hanging by the wrists and electrocution.
Dozens of people over the years have told The Times in detail about their arrests and detentions and the disappearances of their relatives into the maw of the security system, from early 2011 to this month.
The arrests cut across political and socioeconomic lines. Yahya and Ma’an Sharbaji, two brothers, were arrested with a friend, Ghiath Matar, in September 2011, after leading protests in Daraya, a Damascus suburb. They had been part of a Muslim student group arrested years before for activities like holding discussions on liberalizing Islam and working for peaceful change. Mr. Matar’s body was returned to his family with signs of torture; the Sharbaji brothers have not been seen since, according to the family.
In September 2012, Abdelaziz al-Khair, a leftist dissident, disappeared with his stepson Maher Tahan while leaving the Damascus airport, having flown in from abroad for an opposition conference.
His wife, Fadwa Mahmoud, has teamed up with Mr. Sharbaji’s sister Bayan, and other women with missing family members, to fight for the rights of the detained and disappeared.
About 100,000 Syrians are still detained or missing, Ms. Mahmoud said in an interview, which affects perhaps a million family members. When men disappear, women, in a society with laws that privilege male authority, are left in limbo.
“They cannot grieve, they cannot remarry, they cannot sell property, the family has lost their breadwinner,” she said.
It is rare to meet a Syrian refugee family that does not have a detained or disappeared member, and rarer still to find a former detainee who has not been tortured, said Sareta Ashraph, until recently the chief analyst for the United Nations commission.
K.K., a lawyer, was arrested in 2014, two years after he had participated in a demonstration — with government permission — in Aleppo. He had also represented detainees, acidly commenting one too many times on a court system that finished trials in minutes and gave lawyers no access to their clients or the supposed evidence against them.
He described his eight-month ordeal in hours of interviews: daily beatings, cramming into a cell so packed that there was no room to lie down. He spent three months, he said, with personal space smaller than the size of a manhole.
In one of his first interrogations, he said, he was forced to count the blows, reaching 80 before he passed out.
Doused with cold water, he awoke to be hung for hours by his wrists, bound behind his back with handcuffs. Later, he saw a young detainee get doused with kerosene, and set on fire. It took him 20 days to die, untreated, of infection.
The torture went on until K.K. signed a confession of financing “terrorist” demonstrations — entirely fiction, he said, dictated by his captors.
Now K.K. works with other Syrian lawyers and detainees to compile lists of victims, hoping their records will someday make a difference.
Other alleged war crimes take place in full view.
By 2013, bombings of rebel-held neighborhoods by artillery and warplanes had become routine. Hundreds of videos showed mutilated civilians, including women and children, pulled from rubble.
Hundreds of thousands of Syrians have lived under government siege, according to the United Nations, which has been repeatedly denied permission to deliver food and medical supplies. The chemical attacks of 2013, which killed more than 1,400 people in several Damascus suburbs, struck besieged areas like the town of Moadhamiyeh, making treating victims more difficult.