A U.S. Department of Defense (DoD) photo shows the Ohio-class guided-missile submarine USS Michigan (SSGN 727) arriving in Busan, South Korea, on April 25, 2017, for a regularly scheduled port visit while conducting routine patrols throughout the Western Pacific.  (EPA/US NAVY/MC 2ND CLASS JERMAINE RA)

On Wednesday, President Trump will summon the entire Senate to the White House for a special briefing on North Korea.

On Tuesday, North Korea staged artillery drills off its east coast. Off the western coast of the Korean Peninsula, the U.S. and South Korean navies were holding joint military exercises. A U.S. submarine with guided missiles arrived in Busan, South Korea.

Does this type of signaling work? States use many different tools to send firm signals about their international intentions and capabilities. In recent weeks, the Trump administration has sought to “send a message” to rivals through tough actions, such as a missile strike in Syria and dropping the “mother of all bombs” in Afghanistan.

In a recent New York Times article, Max Fisher argued that there is little evidence signals can convey a country’s resolve or that states can establish a global reputation for resolve. Although signaling — particularly when it involves sending messages about different situations in different parts of the world — is indeed challenging, there is actually a large body of evidence that shows that signaling and reputation matter.

But signaling is difficult to pull off effectively. The nature of signals, as well as who does the signaling, is important.

The type of signal matters

Fisher, paraphrasing political scientist Jonathan Mercer, says that a successful signal in international relations must be “precise” and “backed up by action demonstrating capability and intent to follow through.” U.S. troops deployed in South Korea would be a good example.

However, the evidence suggests many other signals might work just as well. In fact, troops might not even be the most effective signal. Matthew Fuhrmann and Todd Sechser find that even a strong signal like deploying nuclear weapons to a “client state” that a major power wants to protect might not be the best option. There’s a better deterrent: simply establishing an alliance agreement between the nuclear power and the client state.

Similarly, in an experiment looking at responses from elite politicians — members of the Israeli Knesset — Keren Yarhi-Milo, Joshua Kertzer and Jonathan Renshon found something surprising. Although both troop mobilization and public threats increase perceptions of others’ resolve, decision-makers didn’t find one type of signal as significantly more credible than the other.

In the same study, they noticed different observers had different views about the type of signal they see as conveying resolve. So hawks tend to view troop mobilization as a more credible indicator than public threats. Doves, on the other hand, viewed threats as the more credible signal.

In a forthcoming book, Roseanne McManus shows that statements designed to show a leader’s resolve can significantly impact the outcome of international military disputes. Elsewhere, McManus also shows a visit by the leader of a major power to a weaker country can credibly signal support for that country — and help deter attacks.

Do facial expressions send messages of resolve?

When he visited South Korea recently, Vice President Pence made a point of being seen out and about along the demilitarized zone (DMZ). Afterward, he declared publicly, “I thought it was important that people on the other side of the DMZ see our resolve in my face.”

A growing body of literature in international relations argues that up-close, expressive signals work. For example, research by Marcus Holmes suggests that national leaders do form impressions of each other’s intentions based on facial expressions.

More broadly, research by Keren Yarhi-Milo shows leaders draw heavily on vivid indicators when assessing the intentions of adversaries. This means they pay attention to face-to-face interactions and other expressive signals such as body language, facial expressions, demeanor and tone of voice.

Nevertheless, expressive signals seem to work when they don’t appear carefully orchestrated, but rather reflect the leader’s true feelings and resolve. Thus, if Pence wants to send signals this way, he would be better off not declaring his strategy. In other words, the first rule of “resolve face” is you don’t talk about “resolve face!”

How can signals of resolve shape high-stakes international disputes?

Reputation matters — that’s the answer many scholars would give. When a leader makes a statement of resolve or a gesture of support for a client state, the leader is putting his or her reputation on the line. Backing down from that message would damage the leader’s credibility.

Several studies have shown that reputations matter. Joshua Kertzer shows that resolve is a personal characteristic, suggesting that some global leaders should have reputations for resolve while others do not. In another study, Alex Weisiger and Keren Yarhi-Milo find that countries that backed down in past crises were significantly more likely to be challenged subsequently. But countries that stood firm in previous crises were far less likely to be challenged in future disputes.

More recently, Danielle Lupton conducted a survey experiment looking at how the statements and behavior of leaders contribute to their reputations. She found that verbal signals of resolve create expectations of future behavior — and initial interactions during a new leader’s tenure are particularly influential to the reputations of new leaders.

In another survey experiment, Jonathan Renshon, Allan Dafoe, and Paul Huth find evidence that both individual leaders and states as a whole can establish reputations.

100 days in, how’s the signaling going?

Although some scholars remain skeptical of the importance of reputation generally and the ability of leaders to signal resolve effectively, a broad view of international relations scholarship offers substantial evidence that when employed skillfully, signals of resolve and reputations for resolve can powerfully affect international affairs.

However, this is not to say that Trump’s signaling strategy will necessarily be effective. Fisher and others have rightly pointed out ambiguity and inconsistency in Trump’s signaling, which might make adversaries uncertain what to believe. This could undermine the administration’s ability to credibly convey its resolve in the future. McManus’s research also suggests that Trump’s domestic political weaknesses may undermine his signaling ability.

So while the Trump administration’s signals of resolve can be effective in theory, his administration has a long way to go to craft an effective signal in practice.

Danielle Lupton is an assistant professor at Colgate University, and her current book project, titled “Leaders, Perceptions, and Reputations for Resolve,” examines how leaders establish reputations for resolve.

Roseanne McManus is an assistant professor at Baruch College, CUNY, and author of the book “Statements of Resolve: Achieving Coercive Credibility in International Conflict,” forthcoming this summer from Cambridge University Press.

 Keren Yarhi-Milo is an assistant professor of politics at Princeton University. She is the author of “Knowing the Adversary: Leaders, Intelligence, and Assessment of Intentions in International Relations” (Princeton University Press, 2014). She has recently completed a new book, “Who Fights for Reputation? Leaders, Resolve and the Use of Force.”