The Central Office for the Investigation of National Socialist Crimes is an austere, pale-yellow prison building nestled into the 18th-century city wall of Ludwigsburg in southwestern Germany. Once used by the Nazis to detain political prisoners, the building announces its contemporary tenants obliquely, with a small, silver sign. Entering the Central Office still feels like entering a jail; to gain access, one must pass through a white metal gate and then through a second secure doorway.

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Since it was created by the West German government in 1958, the Central Office’s mission has been to deliver Nazis to justice. Every year, its six investigative “departments,” each of which consists of a single prosecutor, scour the globe looking for members of the Third Reich. Chief prosecutor Jens Rommel, who heads the operation, is a sturdy, jovial 44-year-old with frameless glasses and a triangular goatee. The German press calls him a Nazi hunter, but Rommel doesn’t like the term. “A hunter is looking for a trophy,” he told me. “He has a rifle in his hand. I’m a prosecutor looking for murderers and I have criminal code in my hand.”

Rommel and his staff visit the sites of former concentration camps across Germany and eastern Europe to sift through records and walk the grounds to determine what defendants might have witnessed from their posts. Over the past decade, the office, which has an annual budget of €1.2m, has also conducted more than 20 trips to archives in South America. The investigators spend most days under an avalanche of bureaucratic documents, checking and cross-checking names on German, Russian, British, French and Polish lists – everything from SS papers documenting quotidian affairs such as the issuing of new uniforms and marriage requests, to Allied inventories of prisoners of war. Their goal is to find the last living Nazis who have yet to be indicted and might still be able to stand trial.

When I visited Ludwigsburg in May, Rommel was preparing for a trip to Moscow, where he would search an archive for names of perpetrators from the Sachsenhausen concentration camp, which the Nazis operated near Berlin from 1936 to 1945. Another Central Office prosecutor, Manuela Zeller, was sorting through records from Auschwitz and Ravensbrück, looking for anyone whose name hadn’t been checked by her predecessors. Her colleague Michael Otte was doing the same for the Buchenwald and Stutthof concentration camps. Another colleague was about to travel to Mauthausen, in Austria, where at least 95,000 people were murdered during the war.

“This is a giant cold-case operation,” Devin Pendas, a historian of Nazi prosecutions at Boston College, said of the Central Office. “It’s looking at crimes that happened a long time ago, with only the sketchiest information about who the perpetrators might be.” Rommel, a former criminal prosecutor, approaches the work the same way he used to investigate homicide cases, treating the archives at his disposal as live crime scenes. “There are crimes behind these words, but there’s no blood here,” he said.

Central Office prosecutors unearth the names of about 30 living perpetrators per year. Their cases are then handed over to regional prosecutors, who usually spend another year conducting follow-up investigations and deciding whether to take the individuals to court. Since the start of the 21st century, this work has led to six prosecutions, but in the media, every case has been called “the last Nazi trial”, as if writers, editors and readers all hope the label will finally prove to be true.

Today, the youngest suspects are 90 years old, and most were low-level Nazi functionaries: guards, cooks, medics, telephone operators and the like. The defendants tend to die during the lengthy judicial process, so the odds of conviction are miniscule. Partly as a result, few Germans know the Central Office exists, and many of those who do tend to view it with ambivalence. “It is hard for people to see what exactly the point is of putting a 90-year-old in jail,” Pendas said. Others view the office with reverence, awed by what it has managed to achieve despite considerable odds.

Throughout its history, the condition of the Central Office has been one important measure of Germany’s evolving relationship to its Nazi past. After its founding in 1958, it enjoyed 10 years of robust activity before receding from public view, amid widespread opposition to further investigations of German war crimes. Now, every day that passes – separating the present from the atrocities in question – further imperils the Central Office’s cause.

Facebook Twitter Pinterest Jens Rommel, chief prosecutor for Germany’s Central Office for the Investigation of National Socialist Crimes. Photograph: Peter Bauza/The Guardian

In Rommel’s corner office, on the second floor of the old prison, 16 small flags, one for each German state, stand atop a wooden bureau. “My bosses,” he said. The 16 regional ministers of justice will soon determine when Rommel’s investigative operation will shut down, ending this global effort to bring Nazi perpetrators to justice. One regional minister told the press that 2025 is a possible deadline for the Central Office to complete its investigations – “‘deadline’ being almost literal,” Rommel told me. Others view that as an optimistic estimate, predicting that the end of the Central Office is much nearer.

The question of whether Nazi trials should continue in spite of the increasingly unrealistic odds of success – whether the work of the Central Office remains essential, or if it needlessly litigates crimes that belong to the past – lingers over the Ludwigsburg headquarters. “How much does Germany need to do to render justice on its own prior crimes?” Pendas said. “And how long does it need to make those kinds of efforts?” These questions have haunted Germany since the war’s end, but have gained renewed currency with the rise of rightwing populist movements such as Alternative for Germany, which may become the third-largest party in the German parliament after the country’s upcoming September election, though the party’s support has declined in recent months. Earlier this year, an AfD politician called for Germany to stop atoning for its Nazi crimes.

Yet the very fact of the Central Office’s continued existence is a testament to the gravity and extent of Nazi crimes, a reminder of just how much is threatened by the rise of reactionary nationalism both in Germany and abroad. In the US, parallel institutions are under threat of closure. The Trump administration has plans to close the State Department’s modest Office of Global Criminal Justice, which is tasked with supporting international prosecutions for perpetrators of war crimes, crimes against humanity, and genocide; its director, Todd F Buchwald, has already been reassigned. As his predecessor, Stephen J Rapp, told the New York Times earlier this year, “The promise of ‘never again’ has proven hard to keep.”

Behind a vault door in the basement of Ludwigsburg’s old prison building lies the Central Office’s “treasure,” as Rommel calls it. In row upon row of beige file cabinets, an ever-expanding archive of 1.7m yellow and green index cards records the names of massacres, battles, concentration camps, victims, witnesses and perpetrators. It is the world’s most comprehensive repository of Nazi crimes and postwar attempts to bring the regime to justice. Anyone who has ever testified or even been mentioned during a Nazi trial has a card, filed in alphabetical order. But the record is not yet complete, and part of the Central Office’s job is to fill in the blanks. “Every day, we add new cards, we change cards,” Rommel said.

Only one copy of the Ludwigsburg archive exists, stored in microfilm at an undisclosed location. Protecting the index is paramount to ensuring war crimes can be tried, and that nothing is forgotten or undocumented – a relatively new undertaking in the history of warfare. For centuries, most peace treaties sought to obliterate the memory of war, a practice stretching back to the 1648 Treaty of Westphalia, which called for “perpetua oblivio et amnestia”, or “perpetual oblivion and amnesty” on both sides. It was only after the 1919 Treaty of Versailles assigned guilt to Germany for igniting the first world war, and demanded the arrest and trial of German officials, that the promise of oblivio et amnestia was abandoned.

Versailles laid the groundwork for the prosecution of war criminals after the second world war, an effort that was well underway even before the Nazis surrendered to allied forces in Reims, France, on 7 May 1945. At the time of his death, a week before the surrender, Adolf Hitler was under indictment by the UN War Crimes Commission, whose members produced hundreds of files documenting his crimes. The commission, which was established in 1943 to investigate offences by the axis powers, also supported indictments against 36,000 German and Japanese personnel, of whom at least 10,000 were convicted in roughly 2,000 trials over the next five years.

These efforts were not universally applauded. Some international participants felt the year-long Nuremberg trials, which culminated in 1946, were a “shocking waste of time”, in the words of Sir Norman Birkett, a British judge who served at the trials. In Germany, the press portrayed the hearings as an attempt to humiliate the country. “If you want to understand why the Central Office was created in the first place, you can see this as a counter-project against Nuremberg,” says Annette Weinke, a historian of post-war prosecutions. “We wanted to take the past into our own hands.”

Between 1945 and 1949, West German courts issued 4,600 convictions for Nazi crimes, but after the creation of the Federal Republic in 1949, a desire for amnesty and oblivion prevailed on both sides of the Atlantic. The UN War Crimes Commission was shuttered and its records sealed, an erasure propelled by the cold war and a rising tide of pro-Nazi sentiment in the US and Germany. As Communists became the greater enemy, the public turned away from reckoning with the Holocaust. Many of the Nazis convicted in the trials that followed Nuremberg were released in the 1950s, when a series of amnesty laws passed by the newly minted West German parliament reinstated the pensions of Nazi soldiers and paroled 20,000 Nazis previously jailed for “deeds against life”. According to the German historian Norbert Frei, nearly 800,000 people benefited from amnesty laws. By the end of the decade, thousands of Nazis had been freed from German prisons and rehabilitated, taking up comfortable posts in the judiciary, police and state administration.

At the same time, however, new trials were gradually opening up the public’s eyes to the enormity of the crimes that had been committed, particularly in eastern Europe. In 1958, during what is now known as the Ulm trial, 10 former policemen from the same mobile killing unit were tried as accessories in the murder of more than 5,000 Lithuanian Jews. Ulm was the first major Nazi trial to take place under West German law, and it exploded “like a bomb” on the German psyche, says Hans-Christian Jasch, director of the memorial site and museum at Wannsee House, where the Nazi leadership discussed the “final solution to the Jewish question” in 1942. Süddeutsche Zeitung, the largest German daily newspaper, carried an opinion piece headlined “Noch sind die Mörder unter uns” (“Murderers are still among us”), calling for more trials. Eager to counter East German propaganda that claimed his government was crawling with former Nazis, chancellor Konrad Adenauer created the Central Office, which was to focus solely on bringing Nazis to justice.

The first index cards were logged at the Central Office when it opened in December 1958. Yet, in truth, the office was never really meant to revise the West German policy of amnesty and reintegration. Its function was intended to be largely symbolic – a kind of alibi for a West German state that wanted to appear as if it were pursuing postwar justice without actually indicting the former Nazis who were once again part of the country’s establishment. As such, the Central Office was denied the ability to prosecute criminals itself. Its work was also hampered by the fact that German law contained no special provision for war crimes, and by a statute of limitations that made certain crimes nearly impossible to prosecute after 1960.

Facebook Twitter Pinterest Central Office prosecutor Manuela Zeller. Photograph: Peter Bauza/The Guardian

When it became known that the office was delivering a spate of names to regional prosecutors, the West German leadership, and the public, was nonplussed. The Central Office’s work was “done against domestic opinion rather than going with it,” Pendas said. Its staffers contributed evidence to the Frankfurt Auschwitz trials, which lasted from 1963 to 1965 and attracted unprecedented coverage in the domestic and international press, but were a “matter of indifference, if not open hostility, for much of the German public,” Pendas has written. When they concluded, pollsters asked the German public whether further Nazi trials should be held. Fifty-seven percent said no.

In 1969, the German high court dealt a blow to the Central Office, when it overturned the conviction of an Auschwitz dentist and former SS member on the grounds that working at the concentration camp was not a crime in itself. As a result, prosecutors were forced to drop an investigation into the Reich Security Main Office, the primary organisation responsible for implementing Hitler’s policy of mass murder. It was a “perpetrator-friendly approach,” Weinke said. “In a way, they were exonerating these crimes.” It also cast the Holocaust, legally and in the public imagination, as a sequence of ordinary murders, replacing the narrative of systematic, state-sponsored genocide with one of individually motivated killings.

After 1969, the work of the Central Office stalled, its prosecutors reduced to chasing the few former Nazi officials whose murderous acts had been recorded on paper. Even though a series of public debates in the 1960s and 70s led to the elimination of the statute of limitations for murder, thousands of men and women who served as cogs in the machine of genocide – as concentration camp guards, doctors, police, administrators and even radio operators – were never forced to reckon publicly with their culpability. For the next four decades, the Central Office largely receded from public view, and many forgot it existed entirely. Then, starting in 2007, a series of landmark cases changed everything.

In January 2007, Mounir el Motassadeq was sentenced by a German court to 15 years in prison. While studying in Hamburg, Motassadeq, a Moroccan national, had wired money to the 9/11 hijacker Marwan al-Shehhi. He was convicted of 246 counts of being an accessory to murder, one for every passenger aboard the four flights that were hijacked that day. The decision had momentous implications for prosecuting Nazis. If Motassadeq could be guilty of helping commit murder, so too could people like John Demjanjuk, a former guard at the Sobibor extermination camp in Poland. Thomas Walther, a lawyer who was working with the Central Office at the time, came up with a strategy to use the same logic to challenge the precedent set in 1969.

Walther’s revelation came just in time for the 50th anniversary of the establishment of the Central Office, which was teetering on the brink of irrelevance, as victims, witnesses and perpetrators began to die of old age. Pursuing Demjanjuk helped justify the office’s continued existence, and Kurt Schrimm, the head of the Central Office at the time, used the case and the anniversary to try to recast the office as a success of the postwar West German government.

Die Zeit called the Demjanjuk trial a “premiere”, because it promised to be the first of many attempts to hold former Nazis accountable for serving in death camps, and the process was avidly covered in the international and domestic media. In 2011, 91-year-old Demjanjuk was convicted of 28,060 counts of accessory to murder – the number of people slaughtered at Sobibor during the four months he served there in 1943 – but the case was still under appeal when Demjanjuk died in a Bavarian nursing home a year later, still a free man. (In Germany, a conviction does not legally hold if an appeal is pending.)

In 2013, a year after Demjanjuk’s death, the Central Office prepared the “Auschwitz list”, consisting of 30 living former Auschwitz personnel who could be immediately tried according to the logic of the Motassadeq ruling. Of these, only five cases made it to court. (The others died, or were deemed unfit to stand trial.) Ernst Tremmel, a former Auschwitz guard, died in 2016, days before he was due to make his first court appearance for 1,000 counts of accessory to murder. His fellow former guard, 95-year-old Reinhold Hanning, was convicted in June 2016 of facilitating more than 170,000 murders, but died on 30 May of this year, days before Germany’s highest court was expected to deny his final appeal. One trial, that of the 96-year-old former Auschwitz medic Hubert Zafke, is still ongoing, but the proceedings have been so poorly handled that the head judge has become the first jurist in history to be dismissed from an Auschwitz trial because of accusations of bias.

Rommel arrived somewhat reluctantly at the Central Office in 2015, in the midst of these cases. He was leaving a comfortable position as a public prosecutor in his hometown of Ravensburg, a stone’s throw from the Alps, where he liked to ski on weekends. But the allure of approaching the past not as history, but as crime, swayed Rommel to take the Central Office helm (that, and the fact that the age of the average defendant meant the job would hardly last for ever). According to Rommel, the government also wanted someone relatively young to head the organisation, “to avoid the impression that they were terminating the work”.

Facebook Twitter Pinterest Central Office prosecutor Michael Otte. Photograph: Peter Bauza/The Guardian

In 2016, Rommel sent 30 cases to prosecutors. That same year, Oskar Groening became the first person on the Auschwitz list to be successfully convicted using the precedent set by the Motassadeq case. The long story of Groening’s belated sentencing captured something of the agonising history of trying to bring Nazis to justice. Groening’s name was on the final 1948 UN War Crimes Commission list of Polish indictments concerning Auschwitz. But after the commission was dissolved, none of the allied powers provided the Central Office with a copy of the 36,000 indictments the commission processed. (It received a digital copy sometime in the 1980s.)

For the rest of the 20th century, Groening’s guilt was not widely known. Then, in 2005, the former “bookkeeper of Auschwitz” agreed to be interviewed by Der Spiegel. Groening spoke at length about how he sorted through Jewish inmates’ belongings, confiscated their money, and heard their screams emanating from gas chambers. “I would describe my role as a ‘small cog in the gears’,” he said. “If you can describe that as guilt, then I am guilty, but not voluntarily. Legally speaking, I am innocent.”

At the time, the Central Office passed along the article to local prosecutors, but neither law enforcement nor the courts were ready to take on what appeared to be an improbable, and perhaps unpopular, battle. After Motassadeq, however, sentencing Groening seemed not just possible, but prudent.

The final judgment against Groening bought the Central Office a bit more time. Without Groening’s conviction, “our work would have stopped,” Rommel said. Instead, the threshold for guilt had been substantially lowered, and 70 years after the crimes in question, it was once again possible to hold cogs accountable. Groening was 20 when he joined the SS; he is now 96, and in August, prosecutors in Hanover, his home region, deemed him fit to serve his four-year-prison sentence.

In March, I followed Manuela Zeller and Michael Otte, the Central Office prosecutors, to Buenos Aires, where they were trying to complete a database of Nazis who escaped to Argentina after the war. They went with little hope of finding living suspects – no indictments have come out of more than 20 expeditions to archives in Brazil, Peru, Chile, Argentina and Paraguay. A few years ago, they identified a former concentration camp doctor who fled to Peru, but it turned out he was already dead. Given the dismal track record, Zeller and Otte’s trip was primed to be the organisation’s final mission to South America, the culmination of more than a decade of scouring the continent.

“The point of the work is not always to put someone in front of a judge, but also being able to close an archive and say, ‘OK, now we know,’” Otte, a trim, bald prosecutor, explained to me over dinner in Buenos Aires’s antique San Telmo district. “It’s for future generations to know what happened.” The record will never be complete, nor will the Central Office get the chance to check archives in every country where Nazis are known to have fled. “We tried to get into Paraguay, but they said: ‘We have no Nazis here,’” he told me.

The apparent fruitlessness of the Central Office’s expeditions has not escaped scrutiny in the German press. Before Rommel took over in 2015, Die Welt, a conservative broadsheet, ran an article criticising the organisation’s expenditures, under the headline “German Nazi Hunters on Holiday in South America?” It was accompanied by a stock photograph of beachgoers in Rio de Janeiro.

Another common refrain among detractors is that the Central Office’s work could have been completed decades ago. “What I started doing in 2008, they could have done 30 years before,” said Thomas Walther, the lawyer who pressed the Central Office to take up the Demjanjuk case. Law is open to constant reinterpretation and revision; someone could have challenged the high bar for Nazi prosecutions long before the Motassadeq verdict, but, astonishingly, no one thought of it, or dared to try. If they had, it might still have been possible to find and try living offenders around the world; these days, it’s almost certainly impossible.

Although the promise of prosecution has been virtually extinguished, naming every as-yet-unknown name is not futile. Rommel is all too aware of the belatedness of his efforts, and the fact that time is running out. But he is also driven by a sense of finality – the knowledge that if the Central Office does not complete its inventory of Nazi perpetrators, no one will. Collecting the evidence is physically strenuous, mentally exhausting work, but it is perhaps the only thing, short of a trial, that can approximate justice. “Even if we don’t get a lot of perpetrators now, it’s important both for the survivors and their relatives, and for German society as well,” he told me in Ludwigsburg. “I think that’s why all of my colleagues are here, to try to do what’s possible today.”

Two days after our dinner in Buenos Aires, I found Otte and Zeller in an old dormitory on the top floor of the Hotel de Inmigrantes, a sprawling, spare complex that opened in 1911 to accommodate thousands of immigrants arriving from the Old World, and now also serves as a museum. The dormitory had been converted into an archive and working immigration office, its walls lined with 20th-century ship ledgers from around the world. Displayed on one side of the room were European ship manifests from between 1939 and 1968 – a record of every individual who arrived at the port seeking asylum, opportunity and, all too often, a place to hide.

Hugo Mouján, the museum’s press manager, laid out Adolf Eichmann’s landing record. The logistical mind behind the Holocaust had arrived at the Hotel de Inmigrantes in 1950, under the alias of Ricardo Klement. One year prior, the Auschwitz physician Josef Mengele, who performed deadly experiments on prisoners, had also passed through the hotel’s doors. Mouján laid out Mengele’s landing record, browned and frayed, documenting his arrival under the alias Helmut Gregor. The success of the Central Office’s current expedition relied on a single, simple assumption: unlike high-ranking Nazi officials such as Eichmann and Mengele, lower-ranking SS members did not expect to be held accountable for their sins, so they did not bother concealing their identities upon arriving in South America.

Facebook Twitter Pinterest Archive materials at the Hotel de Inmigrantes museum in Buenos Aires. Photograph: Peter Bauza/The Guardian

Zeller and Otte spent the next two weeks poring over passenger lists from between 1959 and 1962, recording the names of every German who could have served the Nazi regime and who could still be alive. Zeller, a former Bavarian judge who has a short black bob and triple ear piercings, had made herself a cheat sheet. The men and women she was looking for must have been born between 1918 and 1931 (14 is the German threshold for criminal culpability, and the Central Office will not open cases against anyone over 99), which means they would have been between 28 and 44 years old upon arriving in Buenos Aires between 1959 and 1962. Every time she and Otte came across a German name that fit those parameters, they wrote it down on a plain piece of A4 printer paper, noting the individual’s nationality, age and hometown.

Standing under a crucifix at the doorway to the archive, arms folded, Zeller reflected on the prevailing public criticism of the Central Office. “They say: ‘Why now, when we have only the little ones, and the others have never been charged?’ But I think that’s no reason to let them all go untouched.”

By the end of their trip, Otte and Zeller had collected more than 1,000 names of potential perpetrators. It will take about 12 months for the Central Office staff to cross-check them against the names in the basement archive. If a name from Buenos Aires happens to match that of an SS officer, Otte will open an investigation. But even if some suspects are alive today, they may not be a year from now.

On their last work night in Buenos Aires, Otte and Zeller seemed at peace with the limited nature of their mission. They said knowing that they’re probably the last ones to do their work – the clean-up crew for one of history’s darkest episodes – makes the job a little easier to bear; the march of time lends it renewed urgency, the impending conclusion endows it with heightened integrity.

“It’s all maybe for nothing – we know that,” Zeller said. “The point now is to say we’ve left nothing out.”

In an 18th-century gatehouse next to the old prison building in Ludwigsburg, a replica of the office of one of Rommel’s earliest predecessors is visible beneath a transparent floor. The exhibit conveys the slow, analogue nature of the postwar pursuit of justice. Stacks of files line the walls; the desk is littered with books, paper and stamps; a binder lies open to a page full of portraits of notable Nazi officers. Leather belts hang from pegs on the wall, ready to be used in binding thousands of pages of evidence. Today, boxes rather than belts are used to store files from the few cases that see the inside of a courtroom. Their slow accumulation has begun to transform the former prison into a labyrinthine memorial to the victims of the Holocaust.

Despite its imperfect mandate and modest findings, the Central Office provides a model for the expiation of national wrongs, acting as a precedent for countries that might be compelled to re-evaluate the past not as history, but as crime. A research institute and federal archive already share the building with Rommel and his team; when it becomes impossible to justify opening any further cases, they will likely subsume the investigative wing. “Criminal justice will hand the baton over to history,” says Lawrence Douglas, a professor of law and jurisprudence at Amherst College.

For the first time, the past will be past, the crime scene will be closed, and Germany’s effort to convict its own criminals will come to an end. Other nations, reckoning with their own wrongdoings, have been far hastier to arrive at this point. As Dan Plesch, author of a new history on the UN War Crimes Commission, put it, “Right now, you see a German chancellor and public who are ironically more alive to the dangers, more willing to share the past, than some of the countries that fought them.”

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Rommel and his staff are keenly aware that some in Germany would like to see the Central Office’s closure expedited, including those who think the office’s efforts to prosecute Nazi telephone and radio operators, guards, chefs and medics strain the limits of propriety. The ambivalence with which much of the public views their trials is understandable, Plesch said, “until it becomes the thin end of the wedge for Holocaust denial, which it very often does, and very quickly”. In 2015, when the refugee crisis ignited a wave of xenophobic hate crimes against asylum seekers in Germany, the Central Office received emails and letters from Nazi sympathisers protesting its work.

For now, though, there’s still so much left to be done: “There are still documents which haven’t been put together, there are still matches that can be found,” Hans-Christian Jasch told me after a recent fact-finding trip to Auschwitz. For Rommel, continuing to scour the world for new evidence is “a question of personal guilt and responsibility”, he said. “A lot of my compatriots have preferred to look into the future instead of into the dark past.”

Main image: the Hotel de Inmigrantes museum and archive in Buenos Aires, Argentina, photographed by Peter Bauza for the Guardian

Support for this article was provided by a grant from the Pulitzer Center on Crisis Reporting.

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