Thursday evening — two days after the 15th anniversary of the start of the Iraq War — President Trump tweeted that he would replace his national security adviser H.R. McMaster with John Bolton. The appointment of Bolton, well known for his very hawkish views, immediately sounded alarm bells for those who recalled his role in the Iraq War and who are concerned about U.S. policy toward North Korea and Iran.

Bolton is at the far end of the hawkish spectrum on foreign policy. Trump has expressed mixed views on military force, but Bolton’s views look as if they will dovetail with Trump’s confrontational stance toward both North Korea and Iran. Recently, for example, Bolton penned an op-ed in the Wall Street Journal making a legal case for a first strike against North Korea.

Still, the appointment does not necessarily mean that war is imminent … yet. Here are three ways foreign policy advisers — and especially hawkish advisers — matter.

1. Hawkish advisers can play a large role in foreign policy decision-making.

One basic question is: How much do foreign policy advisers matter? In my own research, I have found that they do, particularly when the president is inexperienced. President George W. Bush’s inexperience effectively delegated enormous power to his foreign policy advisers, with little presidential monitoring or oversight, contributing to the planning failures in the Iraq War.

But research also suggests that hawks play a particularly large role. One reason comes from psychology. As the psychologist Daniel Kahneman and the political scientist Jonathan Renshon have written, “a bias in favor of hawkish beliefs and preferences is built into the fabric of the human mind.” The arguments of hawkish advisers often play into policymakers’ psychological biases and shortcuts — such as over-optimism about potential conflicts or the aversion to cutting losses. As a result, in debates about war, decision-makers are more likely to listen to hawks than doves.

2. But hawks may be less helpful for selling a new war.

A hawk like Bolton might have a more limited role in how others perceive a potential conflict. In research that will be published later this year, I used a survey experiment conducted on a sample of approximately 3,000 Americans to examine how different advisers’ statements about a hypothetical conflict affected public support for war and presidential approval.

I found that whether a hawkish adviser publicly supports or opposes a potential conflict affects both public support for war and public approval of the president. In general, if the president follows any adviser’s advice, approval goes up; if not, it goes down.

But a hawkish adviser’s support or opposition to a potential troop deployment was more important for Democratic presidents, partly because of the stereotype of Democrats as weak on national security. For Republican presidents, a hawk’s statement could still matter but mainly when a hawkish adviser opposed war — primarily because such a stance is surprising. More important for Republican presidents was whether an adviser known for more restrained views on using military force came out in support of the war. This is one reason Colin L. Powell’s public support for the Iraq War was so important to the Bush administration.

In Bolton’s case, his hawkish views, and his history in the Iraq War, likely already influence how others perceive any statements he might make in favor of war. Even if the public does not pay close attention to Beltway foreign policy debates — or even know who Bolton is — members of Congress, who can send important signals to the public about foreign policy, will likely similarly discount his views. After all, Congress didn’t confirm the George W. Bush administration’s nomination of Bolton for U.N. ambassador; he received a recess appointment.


Former U.S. ambassador John Bolton speaks during the CPAC gathering in February in National Harbor, Md. (Alex Wong/Getty Images)

3. Even advisers with strongly biased views can have surprising effects on decision-making.

Bolton’s hawkishness is well known. But an argument made by political scientist Randall Calvert about “biased information” suggests an unlikely, but still possible, way that Bolton might have a surprising effect. Calvert notes that if a decision-maker who favors a policy has two advisers, one neutral and one also predisposed to that policy, it can make sense for the decision-maker to consult the biased adviser.

Why? Because the decision-maker who favors a policy like war is not likely to be swayed by the objective advice from the neutral adviser. But, Calvert writes, “there is always the possibility (small but significant) that the biased advisor … will unexpectedly pronounce policy 1 bad or policy 2 good or both. Such an unexpected finding makes a big impression on the decision maker; it is enough to reverse prior preferences.”

In other words, if Bolton advises against war, Trump would likely sit up and take notice. Of course, there is a big caveat: Calvert assumes the decision-maker is rational, and we do not know if this is true of Trump.

Still, why might Bolton advise against war? Take North Korea. Yes, he has clearly hawkish views on striking North Korea. But some powerful, structural constraints in the North Korean standoff make even hawks leery of starting a conflict, as Michael Horowitz and I wrote here at the Monkey Cage in early January. And as Dan Reiter argued, there are many reasons to think we are unlikely to see a preemptive or accidental war — and, indeed, they have rarely happened.

None of this is to discount or dismiss the effect Bolton could have on U.S. foreign policy. One set of views he shares with Trump is disdain for international institutions, alliances and norms — the often-invisible backbone of much of U.S. foreign policy for the past 70 years. His appointment is likely to lead to the further erosion of U.S. commitments in these areas.

But in the end, U.S. foreign policy the day after Bolton takes over as national security adviser is likely to be only a little more unpredictable than it was the day before.

Why? Bolton himself gave the answer when he said on Fox News yesterday evening that he wasn’t expecting the announcement of his appointment to be that afternoon.

As Bolton will undoubtedly be reminded in the coming months, U.S. foreign policy still rests in the hands, and phone, of Donald Trump.

Note: An earlier version of this article misidentified Daniel Kahneman.