A diplomat disillusioned with US involvement in Afghanistan has become the first US official known to have resigned in protest over the eight-year war, The Washington Post reported on Tuesday.

Matthew Hoh, 36, was the senior State Department official in Afghanistan’s Zabul province, a hotbed for Taliban militants, until he resigned last month. His background in both civil and military fields may have seemed the perfect fit for President Barack Obama’s administration as it steps up its counterinsurgency efforts in the war-torn country.

But in a September 10 letter to the State Department’s personnel chief, Hoh wrote: “I have lost understanding of and confidence in the strategic purposes of the United States’ presence in Afghanistan.

“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,” added the former Marine Corps captain.