Short answers, pulled from the story.
The Khyber Pass is located in Khyber Pakhtunkhwa, Pakistan, spanning approximately 53 kilometers from Jamrud to Landi Kotal. The corridor descends into the Peshawar Valley at Jamrud and rises to a summit at Landi Kotal inside Pakistan, with a lesser section extending another 20 kilometers westwards to the town of Loya Daka in Afghanistan.
The British government of British India controlled the Khyber region after the Second Anglo-Afghan War ended in 1880. The British Indian Army built the heavily engineered Khyber Pass Railway from Jamrud to the Afghan border near Landi Kotal, which opened in 1925.
Following the partition of India in 1947, the Khyber Pass became part of Pakistan. During the War in Afghanistan, the pass served as a major route for resupplying military armament and food to NATO forces in the Afghan theater of conflict since the beginning of the invasion in 2001.
Historical invasions of the Indian subcontinent have been conducted through this route by Darius I, Ardashir I, Shapur I, and Anushirvan, as well as later Mongols such as Duwa, Qutlugh Khwaja, and Kebek. During the Islamic period, Muslim rulers including Mahmud Ghaznavi, Muhammad of Ghor, Timur, Babur, and Nader Shah used the Khyber and nearby passes for their invasions.
A number of locations around the world have been named after the Khyber Pass, from a steep and twisting minor road in Mugdock Country Park near Glasgow, Scotland, to a suburb of Civil Lines in Delhi, India. The pass features in several of Rudyard Kipling's poems, including The Ballad of the King's Jest and The Ballad of East and West, and has been referenced in songs by Tom Cochrane, Ministry, and Pink Floyd.