(CNN) Col. Anwar R. worked for Syria's intelligence services until he defected at the end of 2012. He fled to Turkey and then moved to Europe, joining the ranks of the exiled Syrian opposition. Eventually, however, his history caught up with him.

Anwar R. was arrested in Berlin in February, suspected of crimes against humanity, including the torture of prisoners. He is the first current or former senior Syrian officer to be arrested in connection with the Assad regime's brutal suppression of protests at the start of the country's March 2011 uprising.

He was detained along with another Syrian, identified by German prosecutors as Eyad A., who worked for the regime's intelligence service and is also suspected of involvement in torturing prisoners. Both men face charges in German courts; multiple attempts to reach their lawyers for comment were unsuccessful.

CIJA Director Chris Engels says that as Syria's war winds down, the pursuit of justice against Assad's regime has become more 'urgent.'

A third Syrian was arrested in France on suspicion of crimes against humanity.

The arrests come eight years after the 2011 protests spiraled into a nation-wide bloodbath. Today, the guns on most of Syria's frontlines have fallen silent. Yet these arrests may signal a new phase in this conflict and they are considered the first big catch for the Syrian war's dedicated investigators.

Sometimes known as the "document hunters," these Syrians have been recruited and trained by former war crimes investigators and lawyers to smuggle hundreds of thousands of government documents out of war zones. Often sprinting past explosions and sniper fire to bring the papers to safety, they risk their lives to help hold the perpetrators of war crimes accountable.

The 'document hunters'

"I said goodbye to my wife and children and told them I am no longer yours. I am owned by Syria, by justice," said one investigator who asked to be identified as Adel.

A well-built middle-aged man, Adel is a self-described idealist. A commercial lawyer before the uprising, he has dedicated the last seven years of his life to the pursuit of justice.

"If you think about the work you've done which you would like written on your tombstone, then for me, this is it," Adel said.

"It is an extremely dangerous task because we are not armed," he added. "And you have to preserve (the evidence) like you would protect a baby."

Photos: Syria's civil war, in pictures Displaced Syrian residents wait to receive food aid distributed by the UN Relief and Works Agency at the besieged al-Yarmouk camp, south of Damascus, Syria, on January 31, 2014. According to the UN Envoy for Syria, an estimated 400,000 Syrians have been killed since an uprising in March 2011 spiraled into civil war. See how the conflict has unfolded. Hide Caption 1 of 52 Photos: Syria's civil war, in pictures Hide Caption 2 of 52 Photos: Syria's civil war, in pictures An injured man lying in the back of a vehicle is rushed to a hospital in Daraa, Syria, on March 23, 2011. Violence flared in Daraa after a group of teens and children were arrested for writing political graffiti. Dozens of people were killed when security forces cracked down on demonstrations. Hide Caption 3 of 52 Photos: Syria's civil war, in pictures Anti-government protesters demonstrate in Daraa on March 23, 2011. In response to continuing protests, the Syrian government announced several plans to appease citizens. Hide Caption 4 of 52 Photos: Syria's civil war, in pictures Syrian children walk over bricks stored for road repairs during a spontaneous protest June 15, 2011, at a refugee camp near the Syrian border in Yayladagi, Turkey. Hide Caption 5 of 52 Photos: Syria's civil war, in pictures Jamal al-Wadi speaks in Istanbul on September 15, 2011, after an alignment of Syrian opposition leaders announced the creation of a Syrian National Council -- their bid to present a united front against Bashar al-Assad's regime and establish a democratic system. Hide Caption 6 of 52 Photos: Syria's civil war, in pictures Delegates from Arab League member states and Turkey discuss a response to the government's crackdown in Syria on November 16, 2011. Hide Caption 7 of 52 Photos: Syria's civil war, in pictures Supporters of al-Assad celebrate during a referendum vote in Damascus on February 26, 2012. Opposition activists reported at least 55 deaths across the country as Syrians headed to the polls. Analysts and protesters widely described the constitutional referendum as a farce. "Essentially, what (al-Assad's) done here is put a piece of paper that he controls to a vote that he controls so that he can try and maintain control," a US State Department spokeswoman said. Hide Caption 8 of 52 Photos: Syria's civil war, in pictures Syrian refugees walk across a field in Syria before crossing into Turkey on March 14, 2012. Hide Caption 9 of 52 Photos: Syria's civil war, in pictures Rebel fighters with the Free Syrian Army capture a police officer in Aleppo, Syria, who they believed to be pro-regime militiaman on July 31, 2012. Dozens of officers were reportedly killed as rebels seized police stations in the city. Hide Caption 10 of 52 Photos: Syria's civil war, in pictures A Free Syrian Army fighter runs for cover as a Syrian Army tank shell hits a building across the street during clashes in the Salaheddine neighborhood of central Aleppo on August 17, 2012. Hide Caption 11 of 52 Photos: Syria's civil war, in pictures Family members mourn the deaths of their relatives in front of a field hospital in Aleppo on August 21, 2012. Hide Caption 12 of 52 Photos: Syria's civil war, in pictures A Syrian man carrying grocery bags dodges sniper fire in Aleppo as he runs through an alley near a checkpoint manned by the Free Syrian Army on September 14, 2012. Hide Caption 13 of 52 Photos: Syria's civil war, in pictures Free Syrian Army fighters are reflected in a mirror they use to see a Syrian Army post only 50 meters away in Aleppo on September 16, 2012. Hide Caption 14 of 52 Photos: Syria's civil war, in pictures Smoke rises over the streets after a mortar bomb from Syria landed in the Turkish border village of Akcakale on October 3, 2012. Five people were killed. In response, Turkey fired on Syrian targets and its parliament authorized a resolution giving the government permission to deploy soldiers to foreign countries. Hide Caption 15 of 52 Photos: Syria's civil war, in pictures A Syrian rebel walks inside a burnt section of the Umayyad Mosque in Aleppo hours before the Syrian army retook control of the complex on October 14, 2012. Hide Caption 16 of 52 Photos: Syria's civil war, in pictures An Israeli tank crew sits on the Golan Heights overlooking the Syrian village of Breqa on November 6, 2012. Israel fired warning shots toward Syria after a mortar shell hit an Israeli military post. It was the first time Israel fired on Syria across the Golan Heights since the 1973 Yom Kippur War. Hide Caption 17 of 52 Photos: Syria's civil war, in pictures Smoke rises in the Hanano and Bustan al-Basha districts in Aleppo as fighting continues through the night on December 1, 2012. Hide Caption 18 of 52 Photos: Syria's civil war, in pictures The bodies of three children are laid out for identification by family members at a makeshift hospital in Aleppo on December 2, 2012. The children were allegedly killed in a mortar shell attack that landed close to a bakery in the city. Hide Caption 19 of 52 Photos: Syria's civil war, in pictures A father reacts after the deaths of two of his children in Aleppo on January 3, 2013. Hide Caption 20 of 52 Photos: Syria's civil war, in pictures Syrians look for survivors amid the rubble of a building targeted by a missile in the al-Mashhad neighborhood of Aleppo on January 7, 2013. Hide Caption 21 of 52 Photos: Syria's civil war, in pictures Rebels launch a missile near the Abu Baker brigade in Al-Bab, Syria, on January 16, 2013. Hide Caption 22 of 52 Photos: Syria's civil war, in pictures An aerial view shows the Zaatari refugee camp near the Jordanian city of Mafraq on July 18, 2013. Hide Caption 23 of 52 Photos: Syria's civil war, in pictures The UN Security Council passes a resolution September 27, 2013, requiring Syria to eliminate its arsenal of chemical weapons. Al-Assad said he would abide by the resolution. Hide Caption 24 of 52 Photos: Syria's civil war, in pictures Residents run from a fire at a gasoline and oil shop in Aleppo's Bustan Al-Qasr neighborhood on October 20, 2013. Witnesses said the fire was caused by a bullet from a pro-government sniper. Hide Caption 25 of 52 Photos: Syria's civil war, in pictures Syrian children wait as doctors perform medical checkups at a refugee center in Sofia, Bulgaria, on October 26, 2013. Hide Caption 26 of 52 Photos: Syria's civil war, in pictures An injured man is helped following an airstrike in Aleppo's Maadi neighborhood on December 17, 2013. Hide Caption 27 of 52 Photos: Syria's civil war, in pictures A man holds a baby who was rescued from rubble after an airstrike in Aleppo on February 14, 2014. Hide Caption 28 of 52 Photos: Syria's civil war, in pictures A US ship staff member wears personal protective equipment at a naval airbase in Rota, Spain, on April 10, 2014. A former container vessel was fitted out with at least $10 million of gear to let it take on about 560 metric tons of Syria's most dangerous chemical agents and sail them out to sea, officials said. Hide Caption 29 of 52 Photos: Syria's civil war, in pictures A Free Syrian Army fighter fires a rocket-propelled grenade during heavy clashes in Aleppo on April 27, 2014. Hide Caption 30 of 52 Photos: Syria's civil war, in pictures A giant poster of al-Assad is seen in Damascus on May 31, 2014, ahead of the country's presidential elections. He received 88.7% of the vote in the country's first election after the civil war broke out. Hide Caption 31 of 52 Photos: Syria's civil war, in pictures Rebel fighters execute two men on July 25, 2014, in Binnish, Syria. The men were reportedly charged by an Islamic religious court with detonating several car bombs. Hide Caption 32 of 52 Photos: Syria's civil war, in pictures Photographs of victims of the Assad regime are displayed as a Syrian army defector known as "Caesar," center, appears in disguise to speak before the House Foreign Affairs Committee in Washington. The July 31, 2014, briefing was called "Assad's Killing Machine Exposed: Implications for U.S. Policy." Caesar, apparently a witness to the regime's brutality, smuggled more than 50,000 photographs depicting the torture and execution of more than 10,000 dissidents. CNN cannot independently confirm the authenticity of the photos, documents and testimony referenced in the report. Hide Caption 33 of 52 Photos: Syria's civil war, in pictures Volunteers remove a dead body from under debris after shelling in Aleppo on August 29, 2014. According to the Syrian Civil Defense, barrel bombs are now the greatest killer of civilians in many parts of Syria. The White Helmets are a humanitarian organization that tries to save lives and offer relief. Hide Caption 34 of 52 Photos: Syria's civil war, in pictures Medics tend to a man's injuries at a field hospital in Douma after airstrikes on September 20, 2014. Hide Caption 35 of 52 Photos: Syria's civil war, in pictures A long-exposure photograph shows a rocket being launched in Aleppo on October 5, 2014. Hide Caption 36 of 52 Photos: Syria's civil war, in pictures Rebel fighters dig caves in the mountains for bomb shelters in the northern countryside of Hama on March 9, 2015. Hide Caption 37 of 52 Photos: Syria's civil war, in pictures Nusra Front fighters inspect a helicopter belonging to pro-government forces after it crashed in the rebel-held Idlib countryside on March 22, 2015. Hide Caption 38 of 52 Photos: Syria's civil war, in pictures A Syrian child fleeing the war gets lifted over fences to enter Turkish territory illegally near a border crossing at Akcakale, Turkey, on June 14, 2015. Hide Caption 39 of 52 Photos: Syria's civil war, in pictures A refugee carries mattresses as he re-enters Syria from Turkey on June 22, 2015, after Kurdish People's Protection Units regained control of the area around Tal Abyad, Syria, from ISIS. Hide Caption 40 of 52 Photos: Syria's civil war, in pictures A sandstorm blows over damaged buildings in the rebel-held area of Douma, east of Damascus, on September 7, 2015. Hide Caption 41 of 52 Photos: Syria's civil war, in pictures Members of a Syrian opposition group attack the headquarters of al-Assad regime forces in the Aleppo villages of Nubul and al-Zahraa on February 12, 2016. Hide Caption 42 of 52 Photos: Syria's civil war, in pictures This still image, taken from a video posted by the Aleppo Media Center, shows a young boy in an ambulance after an airstrike in Aleppo, Syria, on August 17, 2016. It took nearly an hour to dig the boy, identified as Omran Daqneesh, out from the rubble, an activist told CNN. The airstrike destroyed his home, where he lived with his parents and two siblings. Director of the Aleppo Media Center Yousef Saddiq said Omran's 10-year-old brother, Ali, died from his injuries. Hide Caption 43 of 52 Photos: Syria's civil war, in pictures Smoke rises after an airstrike in Aleppo on October 4, 2016. Hide Caption 44 of 52 Photos: Syria's civil war, in pictures Arabic writing that reads "some day we will return" is seen on a bus window as civilians evacuate Aleppo on December 15, 2016. The evacuations began under a new ceasefire between rebels and pro-government forces. Hide Caption 45 of 52 Photos: Syria's civil war, in pictures This photo, provided by the activist Idlib Media Center, shows dead children after a suspected chemical attack in the rebel-held city of Khan Sheikhoun on April 4, 2017. Dozens of people were killed, according to multiple activist groups. The United States responded a few days later by launching between 50-60 Tomahawk missiles at a Syrian government airbase. US officials said the base was home to warplanes that carried out the chemical attack. Syria has repeatedly denied it had anything to do with the attack. Hide Caption 46 of 52 Photos: Syria's civil war, in pictures Members of the UN Security Council raise their hands on April 12, 2017, as they vote in favor of a draft resolution that condemned the reported use of chemical weapons in Syria. Hide Caption 47 of 52 Photos: Syria's civil war, in pictures Residents of the war-torn city of Douma break their Ramadan fast on June 18, 2017. Hide Caption 48 of 52 Photos: Syria's civil war, in pictures A member of the Syrian pro-regime forces fires a machine gun as a comrade holds his feeding ammunition belt on November 11, 2017. It was during an advance toward rebel-held positions west of Aleppo. Hide Caption 49 of 52 Photos: Syria's civil war, in pictures A child receives medical treatment after a village was attacked in the rebel-held Eastern Ghouta region on February 25, 2018. Several people were treated for exposure to chlorine gas, opposition groups said, as airstrikes and artillery fire from the regime continued. CNN was unable to independently verify claims that chlorine was used as a weapon. Hide Caption 50 of 52 Photos: Syria's civil war, in pictures Bodies lie on the ground in the rebel-held city of Douma, Syria, on April 8, 2018. According to activist groups, helicopters dropped barrel bombs filled with toxic gas on Douma, which has been the focus of a renewed government offensive that launched in mid-February. The Syrian government and its key ally, Russia, vehemently denied involvement and accused rebel groups of fabricating the attack to hinder the army's advances and provoke international military intervention. Hide Caption 51 of 52 Photos: Syria's civil war, in pictures Damascus skies erupt with anti-aircraft fire as the US and its allies launch an attack on Syria's capital early on April 14, 2018. US President Donald Trump announced airstrikes in retaliation for Syria's alleged use of chemical weapons. Trump says the strikes are part of a sustained military response, in coordination with France and the United Kingdom. Hide Caption 52 of 52

Since 2012, the Commission for International Justice and Accountability (CIJA) has sought to ensure that evidence of alleged war crimes in Syria is compiled and preserved for future trials.

A non-profit organization funded by Western governments, CIJA has acquired over 800,000 Syrian intelligence and security documents. Over the last four years, it has used these papers to build cases against senior and former officials implicated in some of the regime's most brutal human rights abuses.

The Syrian government did not respond to CNN's request for comment. Syrian officials have repeatedly denied allegations of war crimes and crimes against humanity, insisting that they target terrorists and not peaceful protesters.

Onslaught of bombs and bullets

Investigators like Adel have developed a kind of smuggling playbook. Typically, they hold near the frontlines as a battle rages, waiting for the Syrian military to withdraw from an area, leaving it in rebel hands.

The document hunters would then move into abandoned regime facilities and collect every document that they are able to salvage, retrieving every single paper in order to avoid accusations of selectivity in evidence collection.

But the regime nearly always intensifies its bombardment of areas just after its military retreats. The document hunter must then brave this onslaught of bombs and bullets, attempting to save documents that may otherwise be destroyed by fire or floods.

Several of these smugglers have been detained by warring parties during this process, according to Adel.

Over the last two years, the regime has recaptured most of Syria, making the collection of documents much harder. Yet the evidence still continues to trickle in.

'What we don't get out today ... might be lost forever'

CNN gained rare access to the latest handover of documents near one of Syria's borders.

In November, Adel's team arrived at a secret meeting point in the border region, carrying black garbage bags that concealed the documents. In a few swift movements, Chris Engels, CIJA's Director of Investigations and Operations, shoved the papers into suitcases in the trunk of his car and then took them to a nearby hotel.

"In the past, when the regime was on its backfoot we were able to collect three or four times as much as that in one go," said Engels. "With the Syrian regime taking more and more territory this work becomes much more urgent. We know that what we don't get out today or tomorrow might be lost forever."

This trove of documents is kept in CIJA's secret headquarters in Europe where a team of analysts is translating and logging them. The documents are stored in stacks of boxes in a darkened and heavily air-conditioned room known as "the vault."

Documents taken from Syria's battle zones are stored in an air conditioned 'vault' in a secret European location.

The victims

The cases against suspected war criminals are not solely based on documents, however. They also rely on witness testimony and visual evidence, such as the so-called Caesar photographs . This collection of more than 28,000 images smuggled out by a military defector codenamed Caesar showed emaciated and wounded dead bodies of detainees in regime prisons.

Each corpse had a number on it which CIJA said its investigators were able to match with the data in their smuggled documents. This research helped the organization identify the dead and connect the bodies to individuals who oversaw the detainees' movements.

Stories of the torture and death of peaceful protesters in Syrian regime custody are widespread. Some 82,000 people are believed to have been forcibly disappeared into an abyss of prisons and military intelligence centers over the course of the war, according to the Syrian Network for Human Rights in 2018.

Many former regime prisoners are reluctant to speak out now that Assad has all but declared victory. But for Amina al-Khoulani -- a former detainee and activist who has lost three brothers to regime prisons -- silence is not an option.

While there are no 'smoking guns,' the documents help paint a picture of a brutal crackdown on dissidents ordered from high levels of command.

"They detained me and my husband in front of my mother and children," Khoulani told CNN. A soldier cocked his gun at her mother after they charged in "like monsters," she said. Her frightened 4-year-old daughter, clinging to her mother's leg, wet herself.

During Khoulani's interrogations, she said her husband was brought into the room wearing only his underwear. She was made to watch her interrogators beat him and cover him with cold water, before she signed a forced confession.

"I knew men were being tortured to death, and my husband looked horrible after three days of torture," recalled Khoulani.

After Khoulani's husband was released from prison, the family fled to the UK where they now live with their three children.

For years, she tried to track down news of her brothers Majd and Abdul Sattar al-Khoulani, who were detained in summer 2011, and Mohammed, who was imprisoned in 2012. After paying a number of bribes, she was able to visit Majd and Abdul Sattar in the notorious Saydnaya prison north of Damascus, dubbed by Amnesty International as a "human slaughterhouse."

Khoulani barely recognized her siblings, describing Abdul Sattar as a "walking skeleton." That was the last time she saw her brothers.

In 2015, the image of Mohammed's tortured and lifeless corpse was found among the Caesar photographs. Then, last summer, Amina received the government death notices of Majd and Abdul Sattar. The regime claimed both brothers had died of natural causes, although reports of extreme torture and neglect in regime prisons were well-documented and widespread. According to their death notices, they died at the same hour of the same day, 22:00 on January 15, 2013.

"The (Syrian) regime is the Hitler of our time," said Khoulani. "Bashar al-Assad will be tried. I might not be alive but my children may see that day."

The search for justice

One of the senior regime members targeted by CIJA was Anwar R. Documents showed that the divisions that he ran detained and interrogated opposition activists on a nearly daily basis. Some 6,000 pages of documents smuggled to CIJA detail the workings of his departments, notorious for its torture chambers according to several human rights groups.

One of the security branches he worked at -- Branch 285 -- is headquartered in a five-story building in Damascus with an underground section of 250 solitary confinement cells. Beatings, sexual abuse and electrocution were widely reported to be rampant in these quarters.

The cases built against high-ranking officers, CIJA says, reveal a systematic drive against protests, and marks a significant step towards bringing the Assad regime to justice for crimes it has long been accused of.

"There are very few smoking guns," said Engels. Instead, the documents reveal an organizational structure that clarifies how orders went up and down the bureaucracy.

"Through an understanding of that chain of command we can then tie leadership to the events that happened on the ground," he said.

"Peace is a very important thing if you can stop the killings," Engels added. "But that doesn't mean that justice might not come later ... when the discussion about justice does appear in five or 10 or 20 years, there will be evidence there."

After receiving the crushing news about her brothers last year, Khoulani resolved to stop campaigning against Assad. But her silence was short-lived. She now sees making her voice heard as key to keeping alive the memory both of her brothers and the true history of Syria's war.

"The regime's voice is getting louder," said Khoulani. "If we are silent maybe the version of truth will be distorted. The truth will be buried with us so we need to continue speaking up."