It is a near-forgotten chapter in 20th-century history: the rescue of thousands of Jewish men from the Nazis, brought to a camp on the outskirts of the medieval town of Sandwich in Kent as darkness fell across Europe.

The Kitchener Camp rescue began in February 1939, and by the time war broke out seven months later about 4,000 men – mainly German and Austrian Jews – had arrived by train and boat. Although the story of the 10,000 Jewish children brought to the UK on the Kindertransport is well known, the Kitchener Camp has received much less attention.

“It’s not even well known in [UK] Jewish communities,” said Clare Weissenberg, who has curated an exhibition that opens at the Jewish Museum in London on 1 September.

On 2 September, a blue plaque will be unveiled in Sandwich in the presence of descendants of the rescued men, as well as the son and daughter of two Jewish philanthropist brothers who ran the camp.

An overview of Kitchener Camp near Sandwich, Kent. The large tent was donated by the Jewish Lads’ Brigade, and it is believed it was used as a synagogue. Photograph: Courtesy of the family of Erich Peritz

Among those present will be Paul Secher, whose father, Otto, arrived in May 1939.

“My father didn’t talk about it very much,” said Secher. “I sensed it was a painful subject for him. He managed to escape but his parents and a sister didn’t. The burden must have been immense.”

After the Kristallnacht pogrom in November 1938, when Jews and their property were violently attacked, about 30,000 Jewish men were rounded up and taken to Dachau, Sachsenhausen and Buchenwald concentration camps.

The Central British Fund (CBF), a Jewish aid organisation in the UK now known as World Jewish Relief, persuaded the British government to admit some refugees. Adult men were brought to the UK on condition they would not be granted UK citizenship, they must not work, and they must emigrate onwards to the US, Australia and elsewhere.

The CBF organised transport and rented a derelict army base at Richborough, near Sandwich, to house the men. Their first task was to transform the site into a small town. They built or refurbished 42 accommodation huts, shower and toilet blocks, two synagogues, a medical clinic, a post office and shops. A 1,000-seat cinema was constructed with money donated by Oscar Deutsch, the founder of the Odeon chain.

Many families didn't know much about the Kitchener Camp history. The men didn’t talk about it

The men were not interned; they could request a pass to leave the camp. They played football against local teams, visited nearby beaches, and some illicitly worked for cash on Kent farms. Nine editions of a newsletter, the Kitchener Camp Review, were published.

At the time, the population of Sandwich was 3,500. The arrival of 4,000 refugees could have been overwhelming but they were largely welcomed. Hundreds of people attended concerts performed by refugee musicians, and local children visited the camp to play table tennis.

The men expected their families – parents, siblings, wives and children – to follow them to the UK. Some women were granted “domestic service visas” enabling them to escape the Nazis, but arrivals abruptly ended with the outbreak of war on 1 September 1939.

Nearly all Kitchener men were categorised in tribunals as “friendly aliens”, with the words “refugee from Nazi oppression” stamped on their papers. “Enemy aliens” were interned.

After the start of the war, 887 Kitchener men enlisted in the Pioneer Corps. But after the Dunkirk evacuation in May 1940, public opinion turned against German-speaking refugees, who some suspected of being spies or saboteurs. Those not serving in the war effort were interned or deported to Australia and Canada. The Kitchener Camp was closed.

A quartet practising. Refugee musicians gave concerts for the locals. Photograph: Courtesy of the family of Franz Schanzer

Weissenberg began investigating the camp’s history after she “inherited [my father’s] German suitcase. I saw references to the Kitchener Camp and thought, ‘What on earth is that?’”

She set up a website and began collecting stories and memorabilia from descendents of Kitchener men. “Often they hadn’t talked about it. Many of the men lost wives, children, parents – survivor guilt is a huge thing. Many families didn’t know much about the history,” she said. “As a child [of Holocaust survivors], you knew ... not to ask, almost to protect your parent.”

An exception was Lothar Nelken, who had been a judge in Germany before being stripped of his position under the Nuremberg Laws and interned in Buchenwald concentration camp. “He wrote a diary throughout the war. I grew up knowing about his experiences in Buchenwald. He never kept secrets, he shared his memories,” said his son, Stephen.

On Thursday 13 July 1939, Lothar Nelken wrote: “At around 9pm we arrived in the camp… We were welcomed with jubilation. After supper we were taken to our huts; Hut 37/II. I chose an upper bunk. One hut sleeps 36 men. The beds are surprisingly good. One sleeps as if in a cradle.”

In 1973, Clare Ungerson discovered a plaque in Sandwich, “but the wording was very strange, referring to refugees from Nazi oppression”. The daughter of a German Jewish refugee, Ungerson “realised it must refer to Jews, but I’d never heard of this camp”.

After she retired, she researched and wrote a book, Four Thousand Lives, which is being reprinted this month. In terms of the terrible history of the time, the Kitchener Camp may be a small detail she said, “but it’s not small to the many descendants of Kitchener men, who would not exist if those men hadn’t been rescued”.

The exhibition, entitled Leave to Land: The Kitchener Camp Rescue 1939, will run until 8 September. Through it, said Ungerson, documents and memorabilia kept safe by families for 80 years “will now see the light of day to tell a story that for too long has been relatively unknown”.

Frank Harding, a trustee of The Association of Jewish Refugees , which played a role in funding the exhibition, said: “It is with great pleasure that we are recognising one of the lesser known acts of rescue of Britain’s Second World War history, the remarkable story of the Kitchener Camp through which 4,000 lives were saved. It is recognition too of all those who were involved in its conception and establishment and of those refugees who came here, many of whom went on to serve in the Pioneer Corps.

• This article was amended on 28 August 2019 to add a quote from the Association of Jewish Refugees.