Appointed commander of Belfort in 1870, Colonel Denfert-Rochereau was confronted from November 1870 with the attack and the subsequent siege of the city by the German armies under August von Werder.
Denfert-Rochereau then led with his garrison of 15 000 men (of which only 3 500 were actual soldiers) and the city's population a 103 days resistance against the 40 000 soldiers of Werder.