After toppling the Taliban in 2001-2002, the Americans determined to hold Afghanistan against any return by the Taliban. To this end, they established a host of outposts in the countryside and began training-up a new Afghan national army. This policy began under President George W. Bush and continued during the first term of President Barack Obama.
Thus, in 2006, the American created a network of posts in the Korengal Valley in eastern Afghanistan. Offensive operations against the Taliban would launch from these bases. By 2009 the Americans were re-thinking this plan. In 2010, their effort shifted toward protecting the major population centers. Helmand and Kandahar provinces in the south became major battlegrounds.
In 2014, the coalition of American, Afghan, and NATO troops fighting the Taliban declared an end to major combat operations. The Western troops withdrew to a few major urban areas. Kabul, Kandahar, Kunduz, Jalalabad, and Mazar-i-Sharif have become heavily defended centers. Everywhere else, on-going defense responsibilities fell to the Afghan army. In 2015, the American began urging the Afghans to give up trying to garrison or control areas far from the major cities.
For its part, the Taliban has concentrated its efforts at capturing the little outposts in rural areas. Frequent attacks on isolated posts have inflicted hundreds of casualties on Afghan soldiers every week in recent months. Afghan government forces have been reduced by about 5 percent since Summer 2017. Along the way, the Taliban picked up not only momentum, but also a good deal of arms and equipment.
Afghanistan is divided into 407 administrative districts. By the most recent estimate, the government controls 229 of them, while the Taliban controls only 59. That leaves 119 districts that are considered “contested.” The thing is that almost three-quarters of Afghans live in rural areas. Little more than a quarter live in heavily fortified big cities. Falling back on the cities abandons most Afghans to the Taliban.
Initially, President Trump followed the advice of Secretary of Defense James Mattis Recently, the United States has pressed the Afghan government to follow the Western lead. Afghan army troops are falling back on the cities, leaving the country-side districts to the Taliban. That suggests that the Taliban could soon control almost 180 districts. This would give them near-parity with the government.
People offer the conventional excuses: we’re just regrouping in the cities in order to counter-attack into the rural districts at some point in the future. More honestly stated, falling back on the cities “is a rational approach to secure the cities, and provide the Afghanistan government the political opportunity to work with the Taliban.” That seems to mean that the government has to hold the cities in order to have some valuable chips in negotiations for a “compromise peace.” The Trump administration is trying to begin talks with the Taliban. What can the Afghan government get in such negotiations? What will they have to give? Will the Taliban be content to negotiate on the emerging balance of forces or will they try to erode the security of the cities by attacks? Who will be aboard the last helicopter out of Kabul?
 Thomas Gibbons-Neff and Helene Cooper, “New U.S. Tactic in Afghanistan Urges Retreat,” NYT, 29 July 2018.
 For some sense of why this happened, see Sebastian Junger’s film “Restrepo” (2010) and book War (2010).