The extensive archive contains lists of alleged Nazi war criminals, files of charges brought against them, minutes of meetings, reports, correspondence and trial transcripts.

Speaking to Lawyers Weekly, Dr Melanie O’Brien from the University of Queensland’s TC Beirne School of Law said that the archives contain concrete evidence for war crimes committed during World War II which exist nowhere else.

The legal academic described it as one of the most exciting developments for scholars in the field of international criminal justice in recent times.

“Trial transcripts from many different post-WWII trials, as well as the UNWCC’s operational documents will enable scholars to develop a greater understanding of the creation and process of the post-WWII trials,” Dr O’Brien said.

“This is an important issue, as there has been a great deal of criticism of these trials as ‘victors’ trials’, including for their lack of procedural regulation. These documents will help international law scholars better comprehend the establishment and procedure of the trials,” she said.

Among the thousands of once-suppressed files are some of the first evidence of Holocaust concentration camps, The Guardian reports, including records which show China and Poland were the first nations to call for justice.

The records include detailed evidence from the exiled Czech government about Hitler’s role, including his orders and responsibilities, in the co-ordination and control of Nazi massacres against Czechoslovakian units.

Other files provided by the exiled Polish government to the UNWCC described the gassing of millions of Jews in the Nazi concentration camps at Treblinka and Auschwitz.

“The archive will enable researchers and practitioners to strengthen the proof of the role of commanders as high up as Hitler in committing war crimes and carrying out genocide,” Dr O’Brien said.  

“It may also provide concrete evidence of previously unknown and now named perpetrators, for organisations such as the Simon Wiesenthal Centre and domestic prosecution offices to use in their pursuit of justice for Nazi Holocaust criminals, as the archives contain extensive lists of war criminals including from various death and concentration camps,” she said.

The Independent reported that the documents from the archive also showed the West had a good sense the Third Reich was committing genocide against Jewish people and those of other minorities as early as December 1942.

Less than two years later the Allied forces of Britain, Russia and the US would liberate the Nazi extermination camps.

Professor Dan Plesch, from the SOAS University of London, told The Independent that the archive revealed the major powers had commented on the mass murder of Jews earlier than generally assumed.

“It was assumed they learned this when they discovered the concentration camps, but they made this public comment in December 1942,” Professor Plesch said.

In his capacity as a researcher, Professor Plesch could only access the documents held by the UN in New York with special government authority and consent from the UN secretary general.

The academic has been working with the documents for more than a decade and was instrumental in convincing the UN and various international diplomats to grant public access to the archive. Samantha Power, the US envoy to the UN, is also instrumental in the push for the records to be made public.

Thanks to these efforts, about 900GB worth of documents archived by the United Nations War Crimes Commission are now public.

“The German national authorities were never given access to the archive by the allies after the war. All of this has never seen the light of day,” Professor Plesch told The Guardian.

At the beginning of the cold war in the late 1940s, the decision was made to close the UNWCC, together with the records, with the geopolitical transformation of West Germany as an ally.

A searchable online catalogue of the once-secret records hosted by the Wiener Library in London went live last week.

Online access to individual files will not be possible and those who wish to browse the full archive are free to do so from a terminal within the Weiner Library.

Dr O’Brien added that access to the files was of particular interest to researches interested in suspected Japanese war criminals from the same period.

“There is little published on the Australian post-WWII trials, so these documents will provide a greater understanding of Australia’s actions to ensure accountability for war crimes in the post-war period,” she said.