Commentary My first encounter with Afghanistan was many years ago through Eric Newby’s “A Short Walk in the Hindu Kush.” The book is a hoot, partly because Newby made it quite clear that no walk in the Hindu Kush is short, but mostly because of its dramatization of the encounter between a modern Westerner and the harsh, primitive tribalism of a society caught in the past like a bug in amber. I think my next virtual trip to Afghanistan was through Peter Hopkirk’s riveting book “The Great Game: The Struggle for Empire in Central Asia.” Hopkirk’s account of Maj. Gen. William Elphinstone’s disastrous withdrawal from Kabul in 1842—out of a party of 16,000 precisely one European, William Brydon, an army surgeon, made it out alive—made a deep impression on me. “Where’s the army?” he was asked when, badly wounded, he wobbled into the British garrison in Jalalabad, some 90 miles …