Trader Afzal Baig tugs at his horse, frustrated by its stubborn refusal to take another step along a treacherous, snow-covered mountain pass that is peppered with the skeletons of those who have already failed the journey. The Irshad Pass, a narrow trail more than 16,300 feet above sea level, is part of the ancient Silk Road network, used for centuries by traders from northern Pakistan's Hunza valley to cross the Karakoram mountains into Afghanistan's windswept, barren Wakhan Corridor.