Read: The conundrum facing Democrats about America’s role in the world

Meanwhile, the president and those hoping to replace him face the nearly two-decade dilemma of satisfying their own war-weary public at the potential cost of sacrificing fragile gains bought in tens of thousands of American and Afghan lives and billions of American dollars. America’s presence has its own costs for the Afghans; yesterday, the United Nations reported that the United States and its Afghan allies have killed more civilians so far this year than the Taliban has, as the U.S. pulls back and relies more on air strikes.

Trump isn’t one to dwell on this wrenching problem in public—he recently said he could end the war “in a week” but “I just don’t want to kill 10 million people. Does that make sense to you?” (The population of Afghanistan is about 35 million, per the CIA.)

But the candidate John Hickenlooper is. He took the rare step in a Democratic primary campaign of arguing that Americans have to stay. “You’re looking at the condition of women if we completely pull our troops out of there. You’re going to see a humanitarian disaster that will startle and frighten every man, woman, and child in this country,” he said. “We’re going to turn our backs and walk away from people that risked their lives to help them build a different future?” The Taliban banned women from attending school and working. According to Amnesty International, during the Taliban years “a woman could be flogged for showing an inch or two of skin under her full-body burqa, beaten for attempting to study, stoned to death if she was found guilty of adultery.”

Read: How a forever war ends

The United States is now engaged in direct discussions with the Taliban about a peace deal that, if successful, would likely see its return to participation in government after an American withdrawal. Inevitably, as it leaves, Washington will have less leverage to influence the Taliban’s behavior, including a key demand that the group deny safe haven to militants.

Maybe Trump can keep his promise to extricate U.S troops from Afghanistan and be content to let Afghans deal with the consequences. If not, and if a Democrat defeats him in 2020, the war will stretch into its fourth presidency, and a new president will have to weigh the trade-off between a responsibility to an American public tired of war and what the U.S. owes a country it invaded and promised to rebuild. So far, both promises keep getting broken, and Afghans pay the highest price.