Phillip Carter is a former Army officer and Iraq veteran who directs the veterans research program at the Center for a New American Security.
President Trump named Lt. Gen. H.R. McMaster as his new national security adviser on Feb. 20. He served in the Army for more than 30 years before his post at the helm of the National Security Council. (Peter Stevenson/The Washington Post)

For a generation after losing the Vietnam War, the American military soothed itself with a “stabbed in the back” narrative: If not for meddling politicians, intrusive journalists and a spineless public, the military would have won the war. In his book, “Dereliction of Duty,” H.R. McMaster (then a young Army major) demolished this palliative myth, carefully using historical evidence to show how military leaders failed their troops and their country by remaining silent — or worse — during the escalation in Southeast Asia. Along with other volumes focused on the conduct of the war, McMaster’s work helped reallocate blame for America’s failures in Vietnam to those in uniform who deserved their share of culpability.

In the book, McMaster carefully avoided many of the larger questions raised by his scholarship, such as whether military dissent might have altered the course of the Vietnam War — both as a matter of good historical tradecraft and career savvy. This past week, McMaster, now a three-star general and bona fide hero of the first and second wars in Iraq, was tapped by President Trump to be national security adviser. The big questions he didn’t take on in print 20 years ago now loom large for him and the White House: Can an insular and politicized team make effective national security policy? Should military officers speak up when they see policy going off track? Would it make a difference if they did? And how should civilian officials encourage dissent from the Pentagon?

“Dereliction of Duty” painstakingly dissects four major decisions between 1963 and 1965 that led the United States deeper into Vietnam. McMaster shows how military chiefs failed repeatedly to raise dissenting views about escalation, unable to penetrate the inner sanctums of the White House and meaningfully change the course of the war. In one anecdote, McMaster describes how Army Gen. Earle Wheeler told his staff that he planned to object to President Lyndon B. Johnson’s decision in 1965 to send more troops to Vietnam without calling up additional reservists. But when asked directly by Johnson whether he agreed with the move, Wheeler silently nodded and indicated his assent. Dereliction of duty, indeed.

Part of the problem lay in how both John F. Kennedy and Johnson after him relied on a small, insular, executive committee of political aides and National Security Council staffers to make decisions. This “ExComm” model worked well during the Cuban missile crisis; it broke down during the grinding years of war in Vietnam. Kennedy disdained advice from senior military leaders, in large part because of his World War II experience, as well as his initial involvement with the service chiefs during the Bay of Pigs fiasco and the missile crisis. Johnson trusted his political instincts more than the military leadership. Regardless of the cause, the effect was the same: Senior military officers were cut out of the loop.

McMaster now assumes the role played by McGeorge Bundy in his book, a different one than he has prepared for during his lifetime of military service. But much of the background is similar. Like Kennedy and Johnson, Trump has chosen to make decisions by relying on a small, insular team of political advisers. McMaster knows, even if his new colleagues don’t, that there is a better way to organize the White House and engage the brass in making national security decisions.

The first challenge facing McMaster is to build a White House that works better in its next four years than it did during its first four weeks. So far, his reported first steps suggest he is moving in the right direction, by quietly meeting with the rank and file to learn how Trump’s operation runs before suggesting changes. Among his likely initial moves is to suggest the disassembly of Stephen K. Bannon’s Strategic Initiatives Group, or at least keep it away from national security. The National Security Council is the president’s special staff for national security, and there’s room in the White House for only one.

Second, McMaster must teach Trump to be more disciplined on national security matters — including his tweets, because every word from a president is a statement of U.S. policy. McMaster must also persuade the president and his top aides to listen to military advisers and include them in the most important and sensitive decisions, such as the drafting of executive orders on immigration. Enlarging the decision circle and taking in more data may slow down certain processes, but it is likely to yield better results, especially for high-risk moves such as the Special Operations raid in Yemen that Trump ordered one week into his term. This, too, will be easier said than done, given the insularity and cliquishness demonstrated by the Trump team to date.

Third, and most similar to the problems that his book described, McMaster must build an ecosystem that enables and encourages generals to speak up — and dissent when necessary and appropriate. This goes beyond instilling discipline in the president and his staff or ensuring that the right people are in the room for decisions. McMaster must actively prod Cabinet officials and senior military leaders to express themselves, and he must protect them when their candor upsets the White House political team. This may be his greatest challenge, because of the president’s thin skin. Trump has shown a predilection for lashing out against dissenters — this month, the administration fired a senior National Security Council director for criticizing White House policy and process.

Nonetheless, McMaster must find ways to encourage the participation (and sometimes dissent) he craved in “Dereliction of Duty,” because a healthy civil-military dialectic makes for better national security policy. McMaster will know this better than anyone in the room, based on his research and his combat experience in Iraq and Afghanistan. Our post-9/11 wars suffered in their conception and execution from unhealthy civil-military relations, illustrated most clearly by the endless, dysfunctional debates over troop levels. Those debates boiled over in highly public episodes, such as Gen. Eric Shinseki’s 2003 congressional testimony about how stabilizing Iraq would require hundreds of thousands of troops , or Gen. Stanley McChrystal’s leaked assessment that it would require tens of thousands more troops to improve the situation in Afghanistan. McMaster has inherited the challenge of improving these relations for these wars and for our next conflicts.

Soliciting dissent from senior military leaders — particularly those who serve atop a professionalized all-volunteer force — won’t be easy. By necessity, the American military culture emphasizes duty, loyalty and respect for the chain of command. Dissent and introspection have their place, but these values are subordinated to mission accomplishment. Further, military officers learn, rightfully, that their role in our nation is to obey civilian authority, consistent with their oath to support and defend the Constitution. Although officers can (and do) weigh in on policy through the National Security Council process, the professional ethic at the Pentagon has instilled a norm that their inputs are often muted and deferential. As my Georgetown law school colleague Rosa Brooks noted last year in The Washington Post, officers may challenge unlawful orders, but they will probably not disobey unwise or disagreeable ones, nor publicly dissent. Ultimately, our professional military leaders are likely to salute and follow orders from the president; that’s what they swear to do.

Fortunately, McMaster has already helped his cause. His book helped nudge a significant evolution of the American civil-military ethic after Vietnam. Before that war, most military officers believed in the model articulated by political scientist Samuel Huntington: Civilians made the big policy decisions; generals saluted, took their orders and focused on the “management of violence.” Since Vietnam, military and civilian leaders have come to embrace an “unequal dialogue,” in the words of national security scholar (and prominent “never Trump”-er) Eliot Cohen. These days, senior military leaders, intelligence officers, diplomats and others participate in a give-and-take behind the scenes, ultimately informing and shaping the final decisions made by elected and appointed political leaders.

McMaster stops short in his book of suggesting that military officers know best or that they should dissent publicly when they disagree with policy. He also studiously avoids speculation that military dissent would have meaningfully changed the course of the Vietnam War. Now, he no longer has the luxury of focusing simply on the archival evidence. McMaster must leverage the history he wrote so compellingly about. He, more than most, knows how to do things better this time.