Yet, despite the efforts of England and Russia, the Hapsburg ruler refused to join the allies: he preferred to play the waiting game which had ruined Prussia.[122] The campaign was reopened amidst terrible weather by a daring move of Bennigsen's Russians westwards, in the hope of saving Danzig and Graudenz from the French.

At first a screen of forests well concealed his advance.

But, falling in with Bernadotte near the River Passarge, his progress was checked and his design revealed.

At once Napoleon prepared to march northwards and throw the Russians into the sea, a plan which in its turn was foiled by the seizure of a French despatch by Cossacks.

Bennigsen, now aware of his danger, at once retreated towards Koenigsberg, but at Eylau turned on his pursuers and fought the bloodiest battle fought in Europe since Malplaquet.