On 6 August 2011, a U.S. CH-47D Chinook military helicopter operating with the call sign Extortion 17 (pronounced "one-seven") was shot down while transporting an Immediate Reaction Force attempting to reinforce a Joint Special Operations Command unit of the 75th Ranger Regiment in the Tangi Valley in Maidan Wardak province, southwest of Kabul, Afghanistan.[1][2][3][4] The resulting crash killed all 38 people on board - 25 US Navy Seals, one pilot and two crewmen of the United States Army Reserve, one pilot and one crewman of the United States Army National Guard, seven members of the Afghan National Security Forces, and one Afghan interpreter, as well as a U.S. military working dog.[1][5][6][7][8] At 31 American military personnel killed, the shoot down of Extortion 17 represents the greatest single-incident loss of American lives in Operation Enduring Freedom - Afghanistan, surpassing the sixteen lost in the downing of Turbine 33, a 160th Special Operations Aviation Regiment (Airborne) MH-47, during Operation Red Wings on 28 June 2005.[2]