Trump faces the same question as Bush and Obama in Afghanistan

From today's New York Times' editorial:

Before he agrees to increased troop numbers, Mr. Trump would be wise to order a full assessment of the war to consider whether sending in more Americans can reasonably be expected to succeed in weakening an insurgency that has sprung back after earlier increases of American force.

Unless the Pentagon delivers a strategy that is significantly different from previous ones, Mr. Trump would be sending more men and women into a deadly war zone while, at best, only temporarily delaying Afghanistan’s descent into further chaos and violence.

Actually the question Trump has to answer is bigger than this – one that neither Bush nor Obama ever really answered: what is the mission in Afghanistan? What are the criteria of success and, ultimately, exit? I don't think we've ever had answers to these questions.