Dieter Bührle: Controversial arms dealer

For 34 years Dieter Bührle was the controversial head of the Swiss arms manufacturer Oerlikon-Bührle. He had taken over from his father, Emil Georg Bührle, a German who became a Swiss citizen and built the company up from next to nothing in the early 20th century.

Even though Germany was banned from manufacturing or importing weapons under the Treaty of Versailles following the Great War he made his fortune, and with it his world-renowned modern art collection, by selling arms to the highest bidder, both Britain and Germany, during the Second World War, including anti-tank guns and the famous 20mm Oerlikon anti-aircraft cannon which eventually shot down many allied aircraft.

At one point, in 1940, Oerlikon anti-aircraft guns were manufactured under licence in Ruislip, north-west London, and used by the Royal Navy and the US Navy, but became best known as the armaments aboard Luftwaffe and Japanese warplanes. When his father, a cavalry officer in the Great War, died in 1956, Dieter – German-born but brought up in Switzerland – had no world wars to bring in profits. So Oerlikon-Bührle was forced to deal in "smaller" conflicts, such as the Nigerian Civil War and the South African regime's efforts to maintain apartheid.

Bührle was a staunch supporter of apartheid but his arms sales – illegal under Swiss law but carried out via falsified end-user certificates – caught up with him in 1970. In one of the most dramatic cases in Switzerland's modern history, Bührle, possibly Switzerland's wealthiest man at the time, was convicted of illegal arms-dealing and sentenced to prison for eight months. Friends in high places – the government and the Bundeshaus (the Swiss parliament) – ensured that the sentence was suspended. He also had to pay a SFr20,000 fine, which would barely have covered a few nights with dinner in his plush family-owned Zürich hotel, the Zum Storchen on the Limmat river, favoured by the wealthy, and royals such as Prince Philip.

Even before then, during the Nigerian Civil War of 1968, Bührle's compatriots had been shocked to learn that aircraft belonging to the International Committee of the Red Cross – Swiss-founded and Swiss-led – had been hit by rockets "made in Switzerland", by Oerlikon-Bührle, to be precise. Swiss law specifically banned arms exports to war zones at the time. For many years, Bührle was also a shareholder of Dynamit Nobel and on the board of Swiss Bank Corporation (SBC), a hugely influential organisation in Swiss society which later merged with the Union Bank of Switzerland to become UBS.

Bührle's conviction lost him his place on the SBC board but did not stop South Africa's President, PW Botha, from awarding him the Grand Cross of the Order of the Star of South Africa in 1978 for "excellent meritorious services," i.e. helping the apartheid régime get enough weaponry to keep the black population under control. By then, Dieter Bührle had also bought another struggling Swiss company, Bally Shoes, from a young Swiss entrepreneur, Werner Rey. He helped Bally expand into clothing, handbags and other leather accessories and to gain access to foreign markets, notably the United States (Oerlikon-Bührle later sold Bally, which remains a leading upmarket high street brand).

Oerlikon-Bührle was also behind the development of the Swiss Pilatus PC-7 light training aircraft which soon became known as the "poor man's bomber" in "little wars" around the world. Bührle always insisted that his firm was innocent since the bombs were attached outside Switzerland.

In 1996, a wartime US intelligence report codenamed Safehaven emerged, listing both Oerlikon-Bührle (during the era of Dieter's father) and Bally (when it was still a separate Swiss family firm) as dealing with the Nazis during the war despite Switzerland's official neutrality. Oerlikon-Bührle was accused of "assisting German armaments production and technical research". Bally was accused of buying millions of square feet of leather from the Germans, some of it alleged to have been stolen from Jews who had been sent to concentration camps.

After Dieter's father, Emil Georg, had built up one of the world's greatest collections of modern European art during the war and in the post-war years – mostly Impressionist and Post-Impressionist, including works by Monet, Cézanne, Van Gogh and Degas – questions were raised, particularly by surviving German Jews, about their provenance. Emil Georg's friendship with Hermann Goering, and where Goering himself got his own art collection from, raised many such questions.

Art experts say that Goering's receipts for art works are as rare as some of the works themselves. Nevertheless, art lovers worldwide are grateful that the EG Bührle Collection still exists in the Zürich museum next to his former home, set up by his son Dieter and daughter Hortense. Art lovers can absorb the paintings and let lawyers and politicians discuss the provenance.

The Bührle Collection was famously robbed of four major paintings at gunpoint in 2008. A Monet, a Van Gogh and a Degas were soon found but it was only earlier this year that Cézanne's Boy in a Red Waistcoat, with an estimated value of over $100m, was recovered in Serbia.

When Bührle died the Swiss newspaper Le Temps described him in its headline as "sulfureux" – literally "sulphurous", but with a connotation more of "shady". (The current company OC Oerlikon, based in Pfäffikon, Switzerland, although a descendant of Oerlikon-Bührle, is an entirely rebranded and respected hi-tech innovation firm with 17,000 employees in 38 countries. The name Oerlikon came from a suburb of Zürich).

Dieter Bührle was born in 1921 in Ilsenburg, in the Harz district of Saxony-Anhalt in Germany, now a popular tourist resort thanks to its surrounding mountains, forests and National Park. He was two when his father moved to Zürich to direct the industrial firm Werkzeugmaschinen-fabrik Oerlikon, which had been founded in 1906. All the family would become Swiss citizens. When Emil Georg died, Dieter, a 34-year-old lawyer who had graduated from Zürich University, took over and set up factories in India and Egypt.

With the international arms trade increasingly under scrutiny, apartheid defeated and Nelson Mandela free, the carpet was pulled from under Oerlikon-Bührle's feet. The Swiss-South African Association, a pro-apartheid support group, had described Mandela as "mentally unfit to lead South Africa." Dieter Bührle "retired" – some say he was forced out – in 1990 and focussed on his vineyards in Tuscany. He is survived by his wife and a son and daughter.

Dieter Bührle, industrialist: born Ilsenburg, Saxony-Anhalt, Germany 31 December 1921; married (one son, one daughter); died 9 November 2012.