The watchmaking House definitively leaves the hands of the Breguet family in 1870, a couple of months before the Franco-German war and the fall of the Second French Empire. This political instability has a direct effect on the Parisian business and Breguet is disheartened to observe sales falling. We have to wait until 1900-1914 and the Belle Epoque to reverse this downturn and to see again an evolution of the demand.
Patent of the sidereal timekeeper (February 28).
Breguet still supplied pieces (notably torpedoboat watches) to the navy, and from the 1930s it also became official supplier to the aeronautical industry, developing instruments specifically in response to the requirements of civilian and military aircraft. In this domain, the firm benefited from the kind and generous assistance provided by one of the most outstanding aircraft builders of the time, none other than Louis Breguet, the great-great grandson of Abraham-Louis. This was the time of cockpit chronographs for the young Air France company and a variety of other aeronautical firms including the Société d'Aviation Louis Breguet, and of siderometers (watches showing sidereal time) for military aircrafts.