Will the US officially declare war on Iran by...?

Resolution Criteria

This market will resolve to "Yes" if the United States formally declares war on Iran through an act of Congress between market creation and the specified date, 11:59 PM ET. Otherwise, this market will resolve to "No." To qualify, Congress must pass a formal declaration of war, consistent with its constitutional authority under Article I, Section 8. Authorizations for the use of military force (AUMFs), executive orders, presidential statements, or military actions do not qualify unless accompanied by a formal declaration of war enacted by Congress and signed into law. The resolution source will be a clear consensus of credible reporting.

A formal US declaration of war on Iran by 31 December 2026 is the heaviest-backed outcome in this market, though trading volume across all three outcomes remains heavily concentrated on 'No' resolution. The market requires an act of Congress — not an executive order or military authorisation — to resolve 'Yes.' The United States has not formally declared war on any nation since 1942, making this a historically rare threshold.

Market structure

The market offers three outcomes tied to different resolution windows, all converging on the same strict constitutional criterion: a formal congressional declaration of war against Iran signed into law. Volume is heavily concentrated away from 'Yes' resolution. The resolution source is a clear consensus of credible reporting. The final deadline is 31 December 2026 at 11:59 PM ET. Authorisations for the use of military force and executive military actions do not qualify.

Background

US–Iran relations have been in a state of sustained hostility since the 1979 Islamic Revolution, intensifying through episodes including the 2020 killing of Qasem Soleimani, repeated proxy conflicts across the Middle East, and prolonged disputes over Iran's nuclear programme. Despite periodic military exchanges and elevated rhetoric, no administration has sought a formal congressional declaration of war against Iran. The formal war declaration mechanism — last used during the Second World War — has been effectively replaced in modern US foreign policy by Authorisations for the Use of Military Force, which carry a lower legislative bar and do not satisfy this market's resolution criteria.

Key factors

The primary structural factor is the constitutional requirement that Congress pass, and the President sign, a formal declaration of war — a mechanism unused for over eight decades. For this market to resolve 'Yes,' both chambers of Congress would need to approve such legislation, requiring significant political alignment between the executive and legislative branches. Escalatory triggers that could shift the political calculus include a direct Iranian attack on US forces or territory, a significant escalation in Iran's nuclear programme, or a broadening regional conflict drawing in US allies. Conversely, diplomatic engagement, ceasefire agreements in adjacent conflicts, or domestic political resistance to war authorisation would maintain 'No' resolution. The distinction between a formal declaration and an AUMF is legally and politically significant; even major military engagements — as seen in Korea, Vietnam, Iraq, and Afghanistan — have proceeded without formal declarations of war.

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