A newly made major-general on the outbreak of the Crimean War, Barnard landed in the Crimea in 1854, in command of a brigade of the 3rd, or Sir Richard England's, division of the army, with which he was present during the winter of 1854–5.

After brief periods of command at Corfu, Dover, and Shorncliffe, Barnard was appointed to the staff in Bengal, and reached Umballa, to take over the Sirhind division, towards the end of April 1857, when rumours of impending unrest were gathering fast.

On 10 May occurred the outbreaks at Meerut and Delhi, the vague tidings of which reaching Umballa were at once sent on by Barnard, and gave the first warning of the Indian Rebellion of 1857 to the commander-in-chief, General George Anson, then at Simla.

The military historian John William Kaye commented that the value of Barnard's victory was not to be measured by returns of killed and wounded or captured ordnance.

'It gave us an admirable base of operations—a commanding military position—open in the rear to the lines along which thenceforth our reinforcements and supplies and all that we looked for to aid us in the coming struggle were to be brought.