[2] Foucault was ordered by the French Navy as part of its 1906 programme and was laid down at the Cherbourg Naval Yard in November of that year.

diesel engines for surface propulsion, and electric motors for power while submerged.

[3] At the outbreak of the First World War Foucault was part of the French Mediterranean Fleet, and sailed with that force to the Adriatic tasked with bringing the Austro-Hungarian fleet to battle or blockading it in its home ports.

On 15 September 1916, while on patrol off Cattaro under the command of Lt. L. Devin, Foucault was spotted under the surface by two Austro-Hungarian Lohner L seaplanes.

The seaplanes landed and took the crew prisoner, holding them until the arrival of an Austrian torpedo boat.