The Battle of Bologna was one of the bloodiest military engagements in history and the second-bloodiest in the Imperial Wars after Petrograd. Napoleon's Grand Army and his forced-conscripts from Austria launched a surprise attack against the retreating British as they attempted to set up base in Bologna after their defeat at Malena, resulting in a total rout of the British Army and the deaths of thousands of Napoleon's "expendables." Bologna would result in a backbreaking blow to Britain, which had already suffered grave casualties in Spain, was stretched thin thanks to their war to protect Canada and naval losses at Nourmoitier.