The Mysterious Case of Rudolf Diesel: Genius, Power, and Deception on the Eve of World War I

Brunt lays out the three foremost theories about Rudolf Diesel's disappearance: suicide, accident, or murder. Accidental death is typically dismissed—this explanation was typically a euphemistic way of describing suicide, which was seen as taboo at the time. 

Most accepted is that Diesel died by suicide. However, most of Diesel's friends and colleagues rejected this idea. Moreover, Brunt points out the absence of typical reasons for suicide, such as health or financial problems: Diesel’s health was good (he had recently hiked through the Alps), he was still eager to continue his work, and there was little evidence to indicate that he was bankrupt. Indeed, the lack of such records makes financial problems less believable, given Diesel’s otherwise meticulous record-keeping—plus, Diesel was at the pinnacle of his career and could easily recoup any losses to his fortune. The final argument against suicide is that Diesel didn't leave a note for his family. 

Would-be Diesel murderers John D. Rockefeller and Kaiser Wilhelm II both had the motive, means, and pattern of behavior to make them immediate suspects. The Kaiser was obsessed with keeping diesel engines proprietary to Germany. Rockefeller would go to any lengths, including extreme violence, to suppress competition. For instance, in 1913, when coal miners at Rockefeller's Ludlow mine went on strike, he hired the Baldwin-Felts Detective Agency, which broke the strike with an armored vehicle known as the "Death Special" to break the strike. The diesel engine threatened Rockefeller's assets more than unions.

However, the facts don't support the murder theory. Rudolf Diesel's behavior had become odd in the weeks leading to his disappearance. For example, he burned a stash of papers related to projects he was working on and donated the rest. He walked his son through his house to show him where everything of value was kept. Even the overnight bag he gave to his wife was suspicious—it was filled with cash and a note from Diesel worrying about whether she would choose to join him. All of this suggests he was aware something was going to happen to him. The mysterious telegram, the crew's testimony, and the cabin list of missing possessions also pose a challenge to the theory that Diesel was murdered. Finally, murdering Diesel aboard a British passenger ferry would have made little sense for the American Rockefeller and the German Kaiser.

Brunt proposes an alternative theory: Diesel defected to the UK, motivated by his openly antagonistic relationship with MAN, his rejection of German nationalism, and his overwhelmingly positive public remarks about Britain and Charles Parsons. This theory would require an enormous deception on the part of the British. However, Brunt argues that the evidence surrounding Diesel's disappearance fits this explanation.

This could be why Martha, Rudolf Jr., and Eugen quickly accepted the disappearance as suicide without pushing for an investigation; they shared Diesel’s anti-nationalist politics and would have understood and been sympathetic to his need to defect. In contrast, Heddy and her husband rejected death by suicide as an explanation; their nationalist politics and close ties to the German military may likely have led to them being left out of the deception.

The SS Dresden left from Belgium, a country sympathetic to the British, making it an ideal location to give Britain an operational advantage for the deception. Since the Dresden sailed under a British flag and since the disappearance took place in international waters, there would be little to no investigation to expose the ruse. Possibly, making the defection look like suicide would allow German authorities to save face rather than admit that their top engineer defected on the brink of war. 

Even the choice of travel companions seems deliberate. Carels was sympathetic to the British and could have played a vital role in the deception; his testimony was treated as fact instead of speculation.

Brunt argues that other small details also point to defection as the most reasonable explanation. Diesel’s odd behavior in the weeks before his departure could be explained if he was planning to leave Germany permanently. The likelihood of his body being found 11 days after drowning, still dressed in fine clothes with easily identifiable objects in the pockets, is low; modern experts believe that for drowning victims, clothes break down and rip apart quickly, it is improbable for objects to remain in pockets, and decomposition prevents accurate identification. 

After speaking with Simon Mann, a former member of the Special Air Service and the Scots Guards, Brunt concludes that British intelligence has a long history of organizing operations to deceive foreign powers.

In March 1914, The New York Times reported that Diesel was living in Canada. Another small story published in a British newspaper alleged that Martha had disappeared after exchanging letters with Diesel. The articles led to speculation about Diesel working for Churchill. Retired intelligence officials agree that Diesel could have sailed the Dresden to Scapa Flow, a body of water in northern Scotland, and then continued to Canada to work for Churchill, away from prying eyes. Then, when his work was complete, he would likely have been moved to Australia, the farthest part of the British Empire.

However, the story of Diesel's sudden reappearance stalled out and didn't gain much traction. Brunt posits that this is because the UK government issued a Defense Advisory Notice—an official request to stop reporting in the interest of national security—to suppress the story in the British press. The story was quickly forgotten when WWI broke out less than four months later and war reporting took precedence.

Other details contribute to the Canada hypothesis. On January 1, 1915, American manufacturing firm Bethlehem Steel fabricated parts for diesel-powered submarines and sent them to a secret location in Montreal, Canada, where a group of foreign engineers worked in extreme secrecy under order of Winston Churchill.

The engineering and production of British submarines took place in Canada. The Washington Post reported that 15 submarines crossed the Atlantic, from Canada to the North Sea, for active duty. The Post confirmed that the submarines were diesel-powered. What makes these submarines so interesting is that British and American engineers were not well-versed enough in diesel technology to develop sophisticated, working submarines in the years prior. In 1913, the Admiralty realized the firms working on submarines could not develop them fast enough to be ready for war, so the Royal Navy acquired an Ipswich-based Diesel submarine company founded by Rudolf Diesel and George Carles. However, when the company was sold to Vickers in 1915 for war effort manufacturing, its newfound sophistication could only have come from working with Rudolf Diesel’s level of expertise in diesel technology.

British Intelligence operations from that era accomplished seemingly impossible feats. One example is the WWII deception known as Operation Mincemeat, the origins of which trace back to WWI intelligence plans. Operation Mincemeat involved a corpse dressed as a pilot carrying fake battle plans to misdirect Italian and German troops from the Allies’ invasion of Normandy on D-Day. British Intelligence carefully planted the body to believably wash up near the Balkans. This operation was only made public knowledge when a high-ranking British official publicized his involvement, so it is likely any similar operations would still be classified. Brunt notes that Winston Churchill led the naval intelligence apparatus in WWI and WWII.

After WWI, the Allies decided not to prosecute Kaiser Wilhelm II; following his forced abdication, he lived the rest of his life in the Netherlands.

In 1936, a journalist named Lemuel F. Parton published an article claiming he had met Diesel in 1914. Parton alleges that when reporting on the Panama-Pacific International Exposition, he met a strange man who claimed to have closely consulted in developing diesel engines. Parton decided that the man could only have been Rudolf Diesel, given his intimate knowledge of diesel engines and Diesel's life. However, Parton couldn't unequivocally prove his claim. 

John D. Rockefeller died in 1937, leaving a fortune of $1.4 billion (about $30 billion in 2024), which was more than 1.5% of the US GDP. Because of Rockefeller and other oil barons, petroleum became the dominant fuel of the 20th century; no nation has built a biodiesel infrastructure to support alternatively fueled diesel engines—though Willie Nelson's diesel tour bus famously ran off recycled cooking oil from restaurants. 

Rudolf Diesel's son Eugen became a writer focusing on technology's social and political implications. Heddy and her husband went on to have close ties to the Nazi Party.

Despite Rudolf Diesel’s essential contributions to the world, he has disappeared from the world’s consciousness. For Brunt, it is almost as if he were intentionally scrubbed from history. The Allies won World War I, but gave little credit to the inventor—possibly because he would have been considered a stolen asset, and because anti-German sentiment would have made it difficult to celebrate the Bavarian man. The diesel engine continued to dominate the air, sea, and land markets. 

In 1923, the German companies Benz and MAN successfully created heavy load-carrying trucks with diesel engines; by 1935, nearly all new trucks used this technology. Diesel’s legacy lives on, as almost 100% of goods are transported by diesel power. While Diesel had hoped for his engine to bring peace, boost rural economies, and uplift the working class, it instead became a tool for the military and big industry.

Diesel disappeared before seeing the impact of his work on the world, still wondering whether the diesel engine could ever return to its true purpose and whether people were better off for its invention.