Soviet troops withdrawing from Afghanistan in 1989.CreditSovfoto/UIG, via Getty Images
The American Century
The first American military battle of the 21st century was fought in Afghanistan shortly after the events of Sept. 11, 2001. After nearly 16 years of fighting a shifting host of militant groups and the new Taliban insurgency, and now even a local affiliate of the Islamic State, there is no clear end on the horizon.
Members of the 101st Airborne Division in Paktia Province in 2013.