 Complete the following phrase:  During the 1814 campaign in north-east France at the Battle of Bar-sur-Aube on 27February 1814, Christiani, at the head of a division of the Old Guard, attacked and drove back the Austrians and routed the troops of General Kleist. This feat of arms is quoted by Napoleon in his letters to the Empress. Christiani then defended Montmartre during the 1814 