Wang Son-Taek
US President Donald Trump has recently escalated his rhetoric over the Iran war, using language that is unusually provocative. He warned that Iran could be “sent back to the Stone Age.” In a social media post, he went further, urging Iran to “Open... Strait,” accompanied by insults and threats that depart sharply from any recognizable form of diplomatic language. Defense Secretary Pete Hegseth echoed this tone, declaring that the United States would show “no mercy” and would not consider normal treatment for enemy combatants. These are not simply strong statements. They resemble the language of coercion and intimidation more than that of diplomacy. By any traditional standard, they fall below the threshold of restraint expected in diplomatic communication.
Diplomatic communication is a nuanced language system built on a combination of seemingly contradictory elements such as determination, euphemism, ambiguity, clarity and restraint. It requires such diversity because no party in international politics can fully control the behaviour of others, while multiple audiences closely observe every move. Diplomats must therefore use carefully calibrated expressions that take into account a wide range of possible scenarios. Euphemistic language allows leaders to express firmness without eliminating the other side’s room for manoeuvre. It preserves ambiguity, and with it, the possibility of de-escalation. When such restraint disappears, the risk of escalation rises while the space for negotiation shrinks. Put simply, diplomatic messages are often ambiguous because the essence of international relations is inherently contradictory, yet all parties must coexist.
Trump and Hegseth would likely reject this logic. They may argue that direct language reflects strength and clarity, while euphemism signals weakness or even hypocrisy. They might claim that harsh rhetoric instils fear and therefore strengthens deterrence. In the domestic arena, such language projects the image of a decisive leader willing to confront threats without hesitation. In a media environment driven by attention and speed, sharp and provocative phrases can also function as effective political tools.
These arguments have internal coherence, but they rest on a simplified understanding of international politics. Effective deterrence is not predicated on fear alone. It depends on credibility, capability and predictability. Excessively harsh language can undermine all three. If threats appear exaggerated or unrealistic, they lose credibility. If rhetoric appears impulsive, it weakens perceptions of strategic control. Most importantly, extreme language reduces predictability, making it harder for adversaries to calculate intentions. This uncertainty does not necessarily produce compliance; it can just as easily produce miscalculation.
Fear, moreover, does not reliably produce submission. It can produce resistance, especially when leaders perceive threats as existential. Public humiliation or extreme rhetoric can transform a political dispute into a matter of regime survival, where backing down becomes politically impossible. What is intended as deterrence can instead trigger escalation. There are also costs for third parties, particularly US allies. Allies rely not only on American power but also on its predictability and responsibility. When US leaders use language that appears erratic or excessively aggressive, it creates anxiety among partners and forces Washington to expend additional effort to reassure them.
Historical experience offers clear lessons. During the Cuban Missile Crisis, John F. Kennedy confronted a situation that could have led to nuclear war. His public message was firm but carefully calibrated. He made clear that the United States would not accept the deployment of Soviet missiles in Cuba, yet he avoided emotional or dehumanizing language. At the same time, he preserved space for negotiation, allowing the Soviet Union to withdraw without humiliation. The crisis was resolved not through intimidation alone, but through disciplined communication that balanced firmness with restraint.
By contrast, the language used by George W. Bush in labelling certain states an “axis of evil” narrowed diplomatic space. It transformed complex political actors into moral absolutes, making engagement more difficult and hardening positions. A single phrase reduced flexibility and constrained future policy options. Trump’s own record provides another illustration. In 2017, he warned North Korea of “fire and fury like the world has never seen.” The result was not the submission of Pyongyang but heightened tension and mutual escalation. Tensions on the Korean Peninsula eventually subsided, but only after intense diplomatic efforts were mobilized.
Some may argue that Trump’s rhetoric follows a long American tradition of forceful leadership, pointing to figures such as Theodore Roosevelt or William McKinley. This interpretation, however, misunderstands the nature of their statecraft. Roosevelt famously advised leaders to “speak softly and carry a big stick,” emphasizing restraint in language even while maintaining strength in capability. McKinley pursued expansionist policies, but his public language remained formal and controlled. Neither leader relied on ridicule, emotional threats or coarse expressions to communicate with adversaries. Their strength was expressed through policy and capability, not through the abandonment of diplomatic norms.
These cases point to a consistent lesson. Diplomatic language is not a matter of style or politeness; it is an instrument of strategy. Effective communication requires restraint in tone, precision in meaning and flexibility in interpretation. It must convey resolve without eliminating the possibility of compromise. It must signal strength without provoking unnecessary escalation, and it must maintain credibility by aligning words with realistic intentions and capabilities.
When leaders abandon these principles, they do not simply change the tone of discourse. They alter the strategic environment itself. Harsh and undisciplined language narrows options, increases risks and imposes costs that may not be immediately visible but accumulate over time. It may produce short-term domestic political gains, but it does so at the expense of long-term national interests. In diplomacy, strength is not measured by how loudly a leader speaks, but by how carefully words are used to shape outcomes. The most effective leaders understood this distinction. Restraint in language is not a sign of weakness, but a form of control. And in international politics, control is the essence of power.
— Wang Son-taek is an adjunct professor at Sogang University.
