With the double milestones in Afghanistan of NATO turning over the remainder of its combat role to Afghan government forces and the announced imminent opening of peace talks with the Taliban, it is an appropriate time to note a few lessons demonstrated by this war.
Foreign military expeditions are more likely to be longer and costlier than expected than to be shorter and cheaper. Most Americans would have been astounded back in the autumn of 2001 if told that U.S. troops would still be fighting and dying in Afghanistan more than eleven years later. Other examples come easily to mind, the Iraq War of the past decade being an especially obvious one. An exception to this pattern was Operation Desert Storm in 1991, aided by the clarity and limited nature of the objective of liberating Kuwait.
Finding off-ramps is hard. The initial goals of the intervention in Afghanistan, of rousting the perpetrators of 9/11 from their haven and ousting their then-allies from power, were noble. They were achieved in the first few weeks of the intervention, after which it probably would have been better to declare the operation a success and go home. But mission creep is a ubiquitous phenomenon.
Welcomes get worn out. Afghanistan used to be a rare oasis in the Muslim world of favorable sentiment toward the United States. The dissipation of much of that goodwill is the almost inevitable result of the damage, frictions, and anger that come from foreign occupation and the operations of a foreign military force.