Just as America must come to the painful realization that the Taliban can’t be destroyed, so the militants and their supporters in the Pakistani government must be made to realize that the United States is backing the Afghan government for the long haul.

There’s the legitimate question of whether the Taliban will accept this reduced arrangement. Given that they once ruled the entire country, it’s easy to think that they won’t settle for less. Bumbling American efforts to talk to the Taliban in recent years have shown how readily their leadership can manipulate such openings for their own advantage.

But negotiations can make sense provided they are part of a deeper reconciliation between the country’s factions and the regional powers that have aided them. After all, the Taliban movement is splintered. In Afghanistan’s hinterlands Mr. Ghani will find there are deals to be struck with local commanders and disgruntled tribal chiefs. If he can incorporate such deals into a broader political settlement — a vision that eluded his predecessor, Mr. Karzai — it will be harder for the Taliban to ignore him.

The outlines of a future Afghanistan — one in which the government controls the major cities, and the Taliban and its affiliates, the country’s tribal hinterlands in the south and east — are starting to emerge.