Nationalism is a political ideology that emphasizes loyalty or devotion to a nation-state’s culture and interests to the detriment of other nations. Nationalism is a major motif in The Mysterious Case of Rudolf Diesel. Rising French nationalism resulted in the Diesel family having to flee France during the Franco-Prussian war. Later, Kaiser Wilhelm II promoted German nationalism to continue unifying the new country, building up its military, and securing its place as a major European power. The resulting arms race between Germany and Britain is tied to the outbreak of WWI, and—Brunt argues—indirectly responsible for Diesel’s death or disappearance.

An arms race is, essentially, a competition between nations for superior development and accumulation of military power. The early 20th-century arms race between Britain and Germany serves as the backdrop for the book. Brunt chronicles rising tensions between the two global powers, which end up co-opting technological innovations for their militaries. Both sides relied on Diesel’s engines for sea and land vehicle superiority, and for the development of new fleets such as submarines. As the British navy perfected the dreadnought class of warships, Germany worked to build their own version, the Nassau class, quickly catching up by using diesel engines.