I do not doubt David Brooks' formulation that fighting and winning wars requires tenacity. The question, in a case like Afghanistan, is whose tenacity? David focuses on the president. I'd focus on the American people.
Currently the country is split roughly in half on whether to escalate or de-escalate Afghanistan. That's after eight years of occupation. The time-scale of the minimal task in front of us - to prevent a second Taliban take-over - is a decade more at least. Jon Rauch helpfully elaborates:
The path to a stable Afghanistan -- to a benign central government that can defend itself and control its territory -- is longer than most Americans realize. "We're certainly talking years, and probably decades," Douglass North says.
"It's a daunting process, and it's troubling, because I don't think most people appreciate that you'd be getting into something very costly. You've got to be willing to devote an enormous amount of time and resources."
Obama needs to make a decision not about whether he has the tenacity, but whether the American people and future presidents will be willing to sustain a decades-long occupation of one of the least politically mature cultures in a mountainous and hard-to-reach landscape ... with no guarantee of success even with the largest number of troops now envisaged. I think the question answers itself. But the institutional and political interests in sustaining this endeavor are far too great to resist. So a war with weak public support by a state already bankrupt in a country close to ungovernable will continue.
Which is how empires always collapse.