This week, the U.S. Navy begins hosting the “Rim of the Pacific” exercise (RIMPAC), the world’s largest international maritime exercise. The 27th RIMPAC, held from Aug. 17-31 around the Hawaiian Islands, includes 20 ships from 10 participating countries — but the Navy scaled back to focus on at-sea exercises and forgo the in-port cultural activities to reduce coronavirus risks.

RIMPAC exemplifies defense or military diplomacy — essentially, the cooperative use of the military in peacetime. Such activities include bilateral or multilateral military exercises, exchanges, search and rescue operations or peacekeeping, among many others. The basic idea behind defense diplomacy is to build trust and confidence between countries, with an eye toward preventing conflict.

Defense diplomacy thus turns the traditional use of the military as a coercive tool on its head and emphasizes the military’s diplomatic role. But our research casts doubt on defense diplomacy’s ability to build cooperation and trust among countries.

Does defense diplomacy work?

Why pursue defense diplomacy? One argument is to build ties between militaries that could mitigate conflict. Here’s one ideal scenario: Generals pick up the phone to call their counterparts, whom they met at a military exercise like RIMPAC, to intervene in an escalating conflict.

But it’s unlikely that military leaders would circumvent civilian orders, or convince their adversaries to do so. It is hard to imagine a Chinese military officer calling up and convincing a military friend in the United States to stop freedom of navigation operations in the South China Sea, for instance.

Moreover, policymakers, military leaders and observers often take for granted that defense diplomacy and trust go hand-in-hand, though even advocates of defense diplomacy are not always clear how these exercises build trust. The prevailing assumption is simply that it does. One analysis, for instance, explains that the idea of “military men, talking soldier to soldier, can resolve differences and build trust and understanding where civilian diplomats and politicians become mired in half-truths, evasions and circumlocutions” is “intuitively attractive.”

This assumption ignores that there are different types of trust. The idea of soldiers working together cooperatively in defense diplomacy might reinforce strategic trust, which is about the predictability or credibility of the other party. As soldiers engage in defense diplomacy, these activities become repetitive, increasing strategic trust. This is why the list of countries invited for each RIMPAC changes little between iterations of the exercise.

Another type is moralistic trust, the belief about the good intention of others. We typically think of this as a country’s basic trustworthiness, which, arguably, is more important than strategic trust in preventing conflict. As nations find each other more trustworthy, they have greater confidence that other countries are mindful of interests other than their own, reducing the likelihood of conflict.

Here’s what we found: While defense diplomacy may increase strategic trust, it also may undermine moralistic trust. Defense diplomacy is as competitive as it is cooperative, which means that militaries pursuing their self-interests may undercut any attempt to increase moralistic trust.

How defense diplomacy becomes a competition

Defense diplomacy activities are a way for militaries to compete in terms of demonstrating capabilities, gaining greater prestige and vying to uncover the secret military edge of others.

First, militaries use exercises like RIMPAC to demonstrate how much more capable they are over a potential enemy, in hopes of deterring opponents from challenging them in the future. A country can target its “partners” in defense diplomacy, as well as non-participants.

For example, the United States invited China to participate in RIMPAC for the first time in 2014, as a demonstration of cooperative intentions but also to give Beijing a true sense of the full might of the U.S. Pacific Fleet. Analysts now tout a RIMPAC in the South China Sea as Beijing’s “worst nightmare.”

Second, when militaries exhibit their platforms and assets on the defense diplomacy stage, the display also serves to bolster the country’s international status and prestige. In 2018, the United States “disinvited” China from RIMPAC in a public move to censure Beijing’s behavior in the South China Sea, in stark contrast to the typical aim of cooperative defense diplomacy in preventing conflicts.

Third, at times militaries will try to hide or downplay their own military capabilities during these exercises. That’s to maintain the advantage of surprise, just in case they might have to use their capabilities during an actual conflict. At the same time, they seek to collect intelligence by observing the capabilities of other militaries. During RIMPAC 2016, for instance, China barred Japanese sailors from tours on its warships. The Japanese were allowed to a reception hosted on board a Chinese warship only after pressure from the U.S.

Militaries seldom admit such competition publicly. Since defense diplomacy is about diplomacy at the surface, a lot of communal praise for other militaries in exercises such as RIMPAC is much more common. And, to be sure, defense diplomacy is more than a pretext to collect military intelligence, gain prestige or deter potential adversaries. Rather, all of this happens at the same time militaries are cooperating with each other.

Such competition and cooperation in defense diplomacy are dilemmas that policymakers and military leaders face in building trust. After the United States and China each held separate military maneuvers last month in the South China Sea, what’s the big takeaway from RIMPAC 2020? With Washington again opting not to extend an invitation to China to participate in the RIMPAC exercises this year, the U.S. seems to be making a strong statement about defense, rather than diplomacy.

Jun Yan Chang is an associate research fellow with the S. Rajaratnam School of International Studies in Singapore. Previously from the Republic of Singapore Navy, he participated in RIMPAC 2010.

Nicole Jenne is an associate professor at the Institute of Political Science at the Pontifical Catholic University of Chile. She holds a PhD in international relations from the European University Institute.