These terms were to be in effect until 19 February. Owing to a lack of information about operations in the departments of Jura, Doubs and Côte-d'Or, these areas were exempted from the general armistice terms in order to preserve the fortified region of Belfort, then under siege. The primary source for the extent of the agreement reached on the date of the ceasefire is the diary of the future German emperor Frederick III, based on his contacts with Bismarck.