In 1870 the Emperor Napoleon III entrusted Bourbaki with the command of the Imperial Guard, and he played an important part in the fighting around Metz.

A certain Edmond Régnier, a French businessman with no political background or connections, appeared at Hastings on the 21 September to seek an interview with the refugee empress Eugénie, and failing to obtain this he managed to get from the young Prince Imperial a signed photograph with a message to the emperor Napoleon.

Bourbaki offered his services to Léon Gambetta, a lawyer and republican politician who had proclaimed the Third French Republic in September 1870.

They crossed the western border of Switzerland at Les Verrières, Sainte-Croix, Vallorbe and in the Vallée de Joux at the beginning of February 1871.

Rather than submit to the humiliation of a probable surrender, Bourbaki had delegated his functions to General Justin Clinchant on 26 January 1871, and tried to commit suicide that night.