Campbell had one tremendous source of anxiety. He had to carry his huge convoy of non-combatants, guns, treasure, and material across the slender, swaying line of boats which bridged the Ganges at Cawnpore before safety was reached. That bridge, indeed, formed his only possible line of retreat. If it were destroyed or fell into the enemy’s hands, the tragedy of Cabul—where only one man escaped out of an army—might have been repeated. Campbell had left Windham to guard the bridge and hold Cawnpore, but Windham had only 500 men—a force scarcely stronger in fighting power than that with which Wheeler held the fatal entrenchments—and within easy striking distance was the Gwalior contingent, numbering, with a fringe of irregulars, some 25,000 men, with forty guns, the most formidable and best-drilled force, on the Sepoy side, in the whole Mutiny. At its head, too, was Tantia Topee, the one real soldier on the enemy’s side the Mutiny produced, with quite enough warlike skill to see the opportunity offered him of striking a fatal blow at Campbell’s communications. If Windham’s scanty force had been crushed, and the bridge destroyed, Campbell’s position would have been, in a military sense, desperate, and the tragedy of Cawnpore might have been repeated in darker colours and on a vaster scale. Sound generalship required Campbell to smash the formidable force which threatened Cawnpore before advancing on Lucknow; but Campbell took all risks in order to succour the beleaguered Residency. Having plucked the beleaguered garrison out of the very heart of the enemy’s forces, it may be imagined with what eagerness Campbell now set his face towards Cawnpore again. There was no safety for his helpless convoy till the bridge was crossed. For days, too, all communications with Windham had been intercepted. An ominous veil of unpierced silence hung between the retreating English and their base. Campbell set out from the Alumbagh on the morning of November 27. All day the great column crept along over the desolate plain towards the Ganges. At nightfall they had reached Bunnee Bridge, and that “veil of silence” was for a moment lifted. Or, rather, through it there stole a faint deep sound, full of menace, the voice of cannon answering cannon! Windham was attacked! He was perhaps fighting for his life at the bridge-head! All through the night those far-off and sullen vibrations told how the fight was being maintained, and with what eagerness the march was resumed next morning may be guessed. Forbes-Mitchell relates how Campbell addressed the 93rd, and told them they must reach Cawnpore that night at all costs. The veteran was fond of taking his Highlanders into his confidence; and he went on to explain:—