Who deserves credit for inventing the four-stroke internal combustion engine cycle: Alphonse Beau de Rochas, who patented the concept in 1862 without building an engine, or Nikolaus Otto, who built the first working four-stroke engine in 1876?

Alphonse Beau de Rochas, a French engineer, patented the theoretical concept of the four-stroke engine cycle in 1862 but never built a working engine. Nikolaus Otto built and commercialized the first successful four-stroke engine in 1876, unaware of the Rochas patent, and only lost part of his own German patent years later when Gottlieb Daimler's lawyer discovered Rochas's earlier description while searching for a way around royalty payments.