Contested Imminence: Questioning the Legitimacy of the Iran War Under Article 51

I recently examined the legal basis of the war with Iran under Article 51 of the United Nations Charter, focusing on whether the use of force could be justified as an act of self-defense rather than dismissed as inherently unlawful. That framework does not prohibit war outright. It permits it under defined conditions, most notably that force is used in response to an armed attack or an imminent threat that leaves no reasonable alternative. As established earlier, “the relevant legal question is therefore not whether force has been used, but whether its use falls within the scope of lawful self-defense.”

This week, however, that question has become more complicated. Not in theory, but in practice. The issue is no longer whether a legal pathway exists, but whether the justification presented meets the required threshold.

In a White House press briefing earlier this week, administration officials stated that the President had been advised—based on intelligence and prior negotiations—that Iran posed a credible and potentially imminent threat to U.S. forces and regional allies, with the president believing Iran was “going to strike the United States and our assets in the region first.” This claim aligns directly with the logic required to invoke Article 51. If an attack is imminent, preemptive action can be framed as lawful self-defense.

At the same time, reporting from Reuters presents a materially different picture. According to U.S. officials cited in intelligence briefings to Congress, there was “no sign that Iran was going to attack first” . Importantly, both accounts originate from within the same U.S. national security structure—one reflecting executive interpretation and the other reflecting reported intelligence assessments—indicating that the divergence is internal rather than purely partisan.

This is not a minor discrepancy. It goes directly to the legal standard. An anticipated escalation or possible retaliation does not meet the same threshold as an imminent initiating attack. Additional reporting indicates that Iran was expected to retaliate against U.S. allies in the region if strikes occurred . Retaliation is conditional—it depends on prior action. Imminence, by contrast, requires that an attack is immediate and unavoidable. The difference between those two conditions is the difference between lawful preemptive self-defense and a use of force that falls outside that justification.

The result is a conflict not only on the battlefield, but within the justification itself. One account presents a threat environment sufficient to support preemptive action. The other reflects a level of uncertainty that complicates that claim. Both cannot simultaneously define the same standard of imminence.

This tension is reinforced by broader strategic ambiguity surrounding the conflict. Reporting indicates that policymakers themselves have struggled to define a clear endpoint, describing the outcome as “elusive” while internal discussions continued over how success should be measured . Public statements have also shifted between objectives—preventing nuclear development, degrading missile capability, and demanding “unconditional surrender” . When objectives are unstable or expand over time, the argument that force was necessary at a specific moment becomes more difficult to sustain, weakening one of the core requirements of lawful self-defense.

At the same time, it would be inaccurate to ignore the measurable military effects of the campaign. Defense reporting indicates that Iranian missile activity has dropped by as much as “90%” and drone operations by “95%” from initial levels . These figures point to clear operational success. However, battlefield effectiveness does not resolve the legal question. A successful campaign can still rest on a contested justification.

Nor has tactical success translated into decisive strategic change. Intelligence reporting indicates that the Iranian regime “remains intact” and that “internal dissent has not emerged meaningfully” despite sustained military pressure . This reflects a familiar pattern in modern conflict: external force can degrade capabilities while reinforcing internal cohesion.

Military theory helps explain why these tensions persist. War operates in what Clausewitz described as “a realm of uncertainty,” where incomplete information and adaptive adversaries prevent clean, definitive outcomes . As Lawrence Freedman notes, “success in war is rarely final,” and early gains do not guarantee strategic resolution . Joint doctrine similarly emphasizes that conflict is defined by “continuous interaction… and adaptation,” meaning that each action reshapes the conditions that follow .

Taken together, these dynamics point to a more precise conclusion. The legality of the war does not turn on whether military success has been achieved, nor on whether a justification has been articulated. It turns on whether the threshold for self-defense—particularly the requirement of imminence and necessity—was met at the moment force was initiated.

That threshold remains contested.

The administration has presented a justification consistent with Article 51, grounded in claims of an imminent threat. Intelligence reporting, however, introduces doubt about whether that level of threat was established. Until that gap is resolved, the question of legitimacy cannot be reduced to a simple answer.

It remains an open problem—one defined not by rhetoric, but by whether the conditions for lawful self-defense were actually satisfied.

Bibliography

Clausewitz, C. von. (1976). On war (M. Howard & P. Paret, Eds. & Trans.). Princeton University Press. (Original work published 1832)

Freedman, L. (2013). Strategy: A history. Oxford University Press.

Reuters. (2026, March 2). Pentagon tells Congress no sign that Iran was going to attack U.S. first, sources say. https://www.reuters.com/world/us/pentagon-tells-congress-no-sign-that-iran-was-going-attack-us-first-sources-say-2026-03-02/

Reuters. (2026, March 6). Trump says there will be no deal with Iran except “unconditional surrender”. https://www.reuters.com/world/us/trump-says-there-will-be-no-deal-with-iran-except-unconditional-surrender-2026-03-06/

Reuters. (2026, March 13b). With Iran war exit elusive, Trump aides vie to affect outcome. https://www.reuters.com/world/us/with-iran-war-exit-elusive-trump-aides-vie-affect-outcome-2026-03-13/

Reuters. (2026, March 11). U.S. intelligence says Iran government is not at risk of collapse, say sources. https://www.reuters.com/business/media-telecom/us-intelligence-says-iran-government-is-not-risk-collapse-say-sources-2026-03-11/

U.S. Joint Chiefs of Staff. (2020). Joint publication 3-0: Joint operations. Department of Defense.

Washington Post. (2026, March 16). U.S. intelligence says Iran’s regime is consolidating power. https://www.washingtonpost.com/national-security/2026/03/16/iran-regime-intelligence-irgc-war/

[White House press briefing source — missing metadata → mark as:]

White House. (2026, March 10). Press briefing by Press Secretary Karoline Leavitt. [Transcript source missing]