Andrew Bacevich describes McMaster’s challenge as Trump’s National Security Advisor:

Through an ironic twist of fate, McMaster now finds himself called upon to fill the role of blunt, candid truth-teller for his generation of military officers—and to do so while serving a commander-in-chief who gives little evidence of valuing those qualities. Yet circumstances demand more than mere straight talk. Only by transcending the role of “military strategist” will General McMaster succeed in doing what duty plainly requires: identifying a course that leads away from permanent war and imparts to what remains of U.S. grand strategy a semblance of coherence.

The good news is that McMaster seems well-suited to the first role. He has a record of speaking his mind and telling superiors things that they won’t want to hear. That is a good trait in any adviser, and there clearly needs to be someone at the highest levels of Trump’s administration willing to tell the president the truth rather than indulge his preferences. In that respect, the contrast with Flynn couldn’t be starker. Flynn was not only essentially a Trump loyalist and yes-man from the start, but he was actively misleading Trump with bad information and poor analysis shaped by a warped worldview. Even when Flynn imagined he was telling Trump hard truths, he was usually feeding him nonsense, and unfortunately it was nonsense Trump was only too willing to believe. McMaster has a reputation for at least sometimes breaking with established assumptions, but as far as I can tell he does not break with reality as Flynn routinely did.

As for the second role, I share Bacevich’s doubts that he could or would try to lead the U.S. away from permanent war, but since Trump will be the one ultimately making the decisions it may not matter. There is no evidence that Trump wants to put an end to any of our current wars, and quite a bit more evidence that he doesn’t. Even if he take seriously his throwaway lines about rejecting “nation-building,” that doesn’t tell us whether he thinks the U.S. should get out of the business of wrecking other nations. He ran explicitly on a platform of escalating at least one of the wars that the U.S. is currently fighting, and he never said that he wanted to end the others that the U.S. was fighting or supporting. McMaster can presumably tell Trump why his proposed “safe zones” in Syria would be dangerous and ill-advised, but will he recommend against sending more U.S. forces to fight ISIS or to Afghanistan? I hope so, but I have no reason yet to think that he will.

In the end, the U.S. will only move away from permanent war if Congress and the public consistently demand it, and as Prof. Bacevich pointed out last week Congress appears to have no interest in that. Until they do, there won’t be much pressure on this or any other president to halt our involvement in open-ended and unnecessary wars, and without that pressure the U.S. will keep fighting indefinitely.