In 1841 William Brydon was posted to Afghanistan as the assistant surgeon[2] of Shah Shuja's Contingent—a British officered infantry force recruited in India to provide protection for the British-backed ruler in Kabul.

The nearest British garrison was in Jalalabad, 90 miles (140 km) away, and the army would need to go through mountain passes with the January snow hindering them.

[4] Under the command of Major-General William George Keith Elphinstone, 4,500 British and Indian soldiers plus 12,000 civilian camp followers, including wives and children, set out for Jalalabad on 6 January 1842, on the understanding that they had been offered safe passage.

[2] By the fourth day of the retreat Brydon's regiment had virtually ceased to exist though he himself was fortunate enough to have found some food abandoned by Lady Macnaghten—the wife of the British envoy murdered in Kabul.

On the afternoon of 13 January 1842, the British troops in Jalalabad, watching for their comrades of the Kabul garrison, saw a single figure ride up to the town walls.

Part of his skull had been sheared off by an Afghan sword, and he survived the blow because he had stuffed a copy of Blackwood's Magazine into his hat to fight the intense cold weather.

Upon recovering from his wound Brydon resumed his duties as a regimental surgeon with the "Army of Retribution" under General Pollock, which briefly reoccupied Kabul in September 1842.

Brydon died at his home Westfield near Nigg in Ross-shire[17] on 20 March 1873, and is buried in Rosemarkie churchyard alongside his brother-in-law Donald MacIntyre VC.