Threats delivered with visible anger are significantly more effective at achieving diplomatic objectives than calm ultimatums, according to new research that challenges conventional wisdom about international crisis negotiations.

When Russian President Vladimir Putin pounds the table during a press conference or North Korean leaders use fiery rhetoric, they may be doing more than just venting frustration.

According to groundbreaking research from the University of Pennsylvania, displays of anger substantially increase the credibility of international threats, while calm threats often fail entirely.

The study, published in the American Journal of Political Science in November of 2024, found that leaders who express anger when making threats are up to 15 percentage points more likely to be perceived as meaning what they say than those who deliver identical threats calmly.

More strikingly, threats delivered without visible anger often backfire, actually decreasing an adversary’s perception of the threatening leader’s resolve.

“Public threats may fail to convey resolve unless leaders also express a substantial amount of anger,” writes Dr. Hohyun Yoon, whose findings help explain why seemingly formidable threats from powerful nations sometimes fall flat.

Angry Leaders Win More Often

By meticulously analyzing over 5,800 statements from world leaders during international crises between 1946 and 1996, Dr. Yoon tracked both threats and anger expressions, from direct statements like “we are outraged” to verbal assaults and accusations of wrongdoing.

The pattern was clear: the angrier the threatening leader, the more likely they were to achieve their objectives.

This correlation holds true even after controlling for factors traditionally thought to determine threat credibility, such as military capability, regime type, and crisis severity.

The research explains previously puzzling historical patterns, including why threats from the Soviet Union succeeded at a 58% rate while those from democracies like the United States, United Kingdom, and France succeeded only 36% of the time between 1918 and 2001.

“Humans share a common understanding of the functions of anger,” Dr. Yoon explains, noting that anger expressions are understood across cultural boundaries, making them particularly effective in international diplomacy.

Why Calm Threats Often Fail

The research included a survey experiment with American respondents who evaluated fictional international crises.

When a leader issued threats “in a calm, measured voice,” respondents estimated only a 50.6% probability the leader would follow through.

When the same leader made identical threats while “yelling in outrage,” that probability jumped to 65.2%.

Even more surprising, when participants first received information about a crisis and then learned a leader had issued a calm threat, their assessment of the leader’s resolve actually decreased by 3.2 percentage points — suggesting non-angry threats may undermine credibility rather than enhance it.

“If perfectly rational individuals always carefully calculate costs and benefits, then emotional displays shouldn’t matter,” says international relations expert Dr. Sarah Kramer, who was not involved in the study. “But in practice, humans use anger as a shortcut to assess what others value and how far they’ll go to protect it.”

Real-World Examples

The findings align with historical cases where emotional displays proved consequential.

During the 2011 Libyan civil war, Moammar Gadhafi furiously threatened that he would “die as a martyr” rather than surrender power.

Western observers immediately characterized him as “a dangerous nut” who might “turn himself into a suicide bomb and take his country down with him” — a perception that influenced international intervention decisions.

Similarly, in the lead-up to the Iraq War, Saddam Hussein doubted President Bush’s resolve “because of exaggerated US fears of casualties,” despite acknowledging America’s overwhelming military superiority.

Hussein’s misreading of America’s willingness to bear costs proved catastrophic.

Emotional Intelligence vs. Military Power

The research suggests that in international crises, emotional displays function as what political scientists call “indices” — signals that carry credibility because they are difficult to fake.

Unlike regime type or military capability, anger is intuitive and immediately interpretable, especially in crisis situations where leaders have limited time to process information.

“In the hectic environment of crisis bargaining, leaders look to more interpretable sources of information before assessing their adversary’s costs,” Dr. Yoon writes, explaining why anger might be prioritized over more complex signals.

As social media and 24-hour news cycles provide ever more opportunities to observe leaders’ emotional states, this research suggests diplomats and military strategists should pay closer attention to the emotional tenor of threats, not just their content.

In international relations, how something is said may matter more than what is said — a lesson that could reshape our understanding of crisis diplomacy for decades to come.