Former US marine and foreign service officer Matthew Hoh's letter of resignation from the US state department delivers a shot across the bow of those who would escalate the American combat presence in Afghanistan. "I have lost understanding of and confidence in the strategic purposes of the United States' presence in Afghanistan," Hoh wrote. "I have doubts and reservations about our current strategy and planned future strategy, but my resignation is based not upon how we are pursuing this war, but why and to what end." With Tuesday's attacks making October the bloodiest month for US troops in the country in the eight years since the war began, Hoh's letter is an expression of deep moral conviction, and senior US officials, from ambassador Karl Eikenberry to vice-president Joe Biden,...