The 1814 Campaign opened with an invasion of eastern France by the main Coalition army led by Austrian Field Marshal Karl Philipp, Prince of Schwarzenberg and a second army led by Prussian Field Marshal Gebhard Leberecht von Blücher. The weak French defending forces were pushed back without too much trouble, except for Mortier's guardsmen near Langres. These crack troops made a fighting withdrawal to Bar-sur-Aube where they offered battle in a strong position. Two days after the clash, Emperor Napoleon joined his reeling forces and the major fighting began.