Dr. William Brydon, an assistant surgeon in the British East India Company Army during the First Anglo-Afghan War, becomes famous for being the sole survivor of an army of 4,500 men and 12,000 camp followers when he reaches the safety of a garrison in Jalalabad, Afghanistan.

The 1842 retreat from Kabul, also called the Massacre of Elphinstone's army, during the First Anglo-Afghan War, was the retreat of the British and East India Company forces from Kabul. An uprising in Kabul forced the then commander, Major-General William Elphinstone, to fall back to the British garrison at Jalalabad. As the army and its numerous dependents and camp followers began its march, it came under attack from Afghan tribesmen. Many of the column died of exposure, frostbite or starvation, or were killed during the fighting.At the beginning of the conflict, British and East India Company forces had defeated the forces of Afghan Emir Dost Mohammad Barakzai and in 1839 occupied Kabul, restoring the former ruler, Shah Shujah Durrani, as emir. However a deteriorating situation made their position more and more precarious, until an uprising in Kabul forced Maj. Gen. Elphinstone to withdraw. To this end he negotiated an agreement with Wazir Akbar Khan, one of the sons of Dost Mohammad Barakzai, by which his army was to fall back to the British garrison at Jalalabad, more than 140 kilometres (90 mi) away. The Afghans launched numerous attacks against the column as it made slow progress through the winter snows along the route that is now the KabulJalalabad Road. In total the British army lost 4,500 troops, along with about 12,000 civilians: the latter comprising both the families of Indian and British soldiers, plus workmen, servants and other Indian camp followers. The final stand was made just outside a village called Gandamak on 13 January.Out of more than 16,000 people from the column commanded by Elphinstone, only one European (Assistant Surgeon William Brydon) and a few Indian sepoys reached Jalalabad. Over one hundred British prisoners and civilian hostages were later released. Around 2,000 of the Indians, many of whom were maimed by frostbite, survived and returned to Kabul to exist by begging or to be sold into slavery. Some at least returned to India after another British invasion of Kabul several months later, but others remained behind in Afghanistan.In 2013, a writer for The Economist called the retreat "the worst British military disaster until the fall of Singapore exactly a century later."

William Brydon CB (10 October 1811 – 20 March 1873) was an assistant surgeon in the British East India Company Army during the First Anglo-Afghan War, famous for reportedly being the only member of an army of 4,500 men, plus 12,000 accompanying civilians, to reach safety in Jalalabad at the end of the long retreat from Kabul.