The Diplomatic and Policy Timeline Leading Up to Operation Epic Fury

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On February 26, 2026, Oman’s foreign minister, who was mediating nuclear talks between the United States and Iran, said the latest round had made significant progress and that technical discussions would follow in Vienna the next week. Two days later, U.S. and Israeli strikes began Operation Epic Fury, the military campaign against Iran that President Donald Trump authorized.

Trump said Iran had rejected repeated attempts to make a deal and that the campaign would destroy its missile industry and navy and prevent an Iranian nuclear weapon. Iran’s proposal left room to resume enriching uranium for reactor fuel after a pause, while Trump demanded no enrichment at all, leaving a gap that reported progress in the talks had not closed.

The demands that divided the negotiations

The Arms Control Association describes itself as a nonpartisan organization promoting public support for effective arms control policies.

According to the Arms Control Association, whose analysts called the U.S. terms maximalist, U.S. negotiators demanded that Iran end uranium enrichment, dismantle enrichment facilities, and remove its enriched uranium gas. Enrichment can produce fuel for civilian reactors, but the ability to enrich also raises the question of how quickly a country could produce material for a weapon.

Trump publicly said on February 27 that he would accept no uranium enrichment, in remarks to reporters in Corpus Christi, Texas.

Enrichment increases the share of uranium-235, the type of uranium atom readily split to release energy. Uranium hexafluoride, or UF6, is the gas used in the enrichment process. Commercial nuclear power plants typically use fuel enriched to about 3-5 percent uranium-235; nuclear weapons use uranium enriched to over 90 percent, or plutonium.

Ahead of the February 26 round of talks in Geneva, Iranian Foreign Minister Abbas Araghchi said an agreement was within reach if diplomacy took priority; he denied that Iran would build a nuclear weapon and defended its right to peaceful nuclear technology. The Arms Control Association reported that Iran’s proposed terms still allowed an enrichment program in the future, while the United States insisted on none.

The nuclear talks also addressed only part of the administration’s stated problem with Iran. Trump’s announced objectives included Iran’s missiles, navy and regional proxy forces as well as its nuclear program. The White House could therefore call a nuclear-only bargain insufficient, while critics could argue that even a limited bargain would lower one urgent risk.

Before the strikes, Arms Control Association analyst Kelsey Davenport argued that renewed talks might lower the risk of nuclear proliferation and create conditions for negotiating a longer-term agreement, while acknowledging that success was uncertain. She proposed a temporary freeze on enrichment and renewed access for International Atomic Energy Agency inspectors while the sides negotiated.

What nuclear inspectors could verify

Military attacks in June 2025 had affected Iranian nuclear facilities, according to a February 27, 2026 report by the International Atomic Energy Agency (IAEA). Trump has said the United States “obliterated” Iran’s nuclear program at Fordow, Natanz and Isfahan in Operation Midnight Hammer that June.

The IAEA reported that Iran had not given it the required reports or access to those facilities, so the agency could not verify their status. The agency also said it could not verify the size of Iran’s uranium stockpile at the affected facilities.

The agency’s estimate as of June 13, 2025, was that Iran held 440.9 kilograms of uranium in UF6 enriched up to 60 percent uranium-235. That is a little under half a metric ton of uranium in UF6, rather than the mass of the entire compound; the IAEA reported that it had verified 432.9 kilograms of the estimated 440.9 kilograms. Uranium at that level can technically be used to build a bomb, Davenport wrote. The estimate is dated, however: it does not measure what was in storage on the day of the 2026 strikes. Davenport argued that if Iran’s government changed or the country fell into unrest, an IAEA presence to account for the materials could deter their misuse, diversion or theft and give greater assurance that they were being monitored.

An inspection gap cuts two ways: it leaves more uncertainty about dangerous material, and it limits confident public claims about precisely what Iran had or was doing at that moment. In March 2025, U.S. intelligence assessed that Iran was not building a nuclear weapon, while warning that its enriched-uranium stockpile was unprecedented for a state without one.

The assessment was a snapshot, not a promise that Iran would never decide to build a weapon. The agency’s February 2026 uncertainty likewise was not proof that Iran had already made that decision. An argument for urgency could therefore rest on dangerous capability and poor visibility, without a verified finding that a bomb was under construction.

The last week of diplomacy

In a February 24 address, Trump warned that he would not allow Iran to acquire a nuclear weapon and alleged that it was rebuilding its program. On February 25, the Treasury Department sanctioned more than 30 people, entities and vessels linked to Iranian petroleum sales and ballistic-missile and advanced conventional weapons production under its maximum-pressure campaign. Pressure and negotiation were moving at the same time; the sanctions were not the end of the talks.

Also on February 25, Iranian Foreign Ministry spokesman Esmaeil Baqaei called U.S. assertions about Iran’s nuclear and missile programs lies. Ahead of the February 26, 2026 Geneva round, Oman’s foreign minister met Araghchi to review proposals Iran would present in the negotiations.

The Feb. 26 Geneva meeting, where U.S. Special Envoy Steve Witkoff and Jared Kushner, Trump’s son-in-law, met Araghchi, was the third round of Oman-mediated nuclear talks, the Arms Control Association reported. Oman’s foreign minister met the U.S. delegation separately that morning to discuss Iran’s proposals and the American response and questions. Oman’s account of that meeting said the U.S. side raised questions about the proposals; it did not describe a final rejection.

After that round, Oman said the sides had made significant progress and planned technical talks in Vienna the following week. The United Nations secretary-general welcomed continued talks, urged a durable agreement, and said full IAEA verification was essential. These statements do not show that a deal was imminent; they do show that the mediators and the United Nations still saw a negotiating process in motion. On February 27, speaking to reporters on the White House South Lawn before departing for Texas, Trump said he was "not happy" with the way the talks were going.

Who chose force, and what Congress knew

A March 1 White House statement confirmed that Trump authorized the campaign.

Trump’s March 2 letter reported the February 28 strikes to House Speaker Mike Johnson. In that letter, Trump said repeated diplomatic efforts had failed and threats to the United States and its partners had become untenable. He cited his constitutional authority as commander in chief and chief executive in conducting foreign relations. Federal law separately requires a president to submit a written report within 48 hours of introducing U.S. forces into hostilities when Congress has not declared war.

Reporting a use of force is not the same as Congress voting to authorize it. On February 28, Senate Majority Leader John Thune thanked Secretary of State Marco Rubio for updates throughout the week and said he expected administration officials to brief all senators. On March 4, Sen. Adam Schiff and colleagues argued that continued hostilities required express congressional authorization that the administration had not sought; a majority of Senate Republicans voted that day to block their resolution to require it.

On February 28, House Intelligence Committee ranking member Jim Himes said Rubio had briefed the Gang of Eight. NPR reported, citing Sen. Mark Warner’s spokesperson, that Rubio notified Warner before the strikes.

The legal and political dispute is therefore about more than notice: it is about how long a president may sustain hostilities without an affirmative vote from Congress. Congress later voted on measures directing the removal of U.S. forces from hostilities with Iran, according to a September 2026 Congressional Research Service report.

The House approved three such concurrent resolutions, on June 3, July 23 and September 15. The Senate agreed to H.Con.Res. 86 on June 23 by a vote of 50-48. These were votes about forces already in hostilities, not a prior vote authorizing the February 28 operation.

The May 19 vote on S.J.Res. 185 was a 50-47 vote to discharge it from committee, a step that placed the proposal on the Senate calendar. On June 24, the Senate rejected a motion to consider S.J.Res. 185 by 47-50. S.J.Res. 185 did not become law.

A concurrent resolution does not go to the president for a signature and does not have the force of law. The War Powers Resolution provides for withdrawal through a concurrent resolution, but the Congressional Research Service says that provision’s constitutional validity is doubtful after the Supreme Court’s 1983 legislative-veto decision in INS v. Chadha.

The case for force and the case for more talks

On March 2, Trump called the operation a response to grave threats and said Iran had ignored warnings not to rebuild its nuclear program. The White House later restated its goals as dismantling Iran’s missile production and naval capability, severing support for regional proxy forces, and preventing a nuclear weapon. The enrichment dispute, the limits on verifying nuclear material and Iran’s broader military capabilities were all part of the unresolved security picture, even with technical talks scheduled for the following week.

Oman’s report of progress does not dispose of that argument: progress in a negotiation can coexist with a threat that officials consider urgent. The open factual question is what the administration knew about that urgency beyond the evidence it made public.

After the strikes began, Oman warned that the conflict could widen across the region and called for it to stop. A diplomacy-first critic can point to that warning, to Oman’s February 26 report of significant progress, to the absence of a documented final rejection in Oman’s account, and to the proposed freeze and inspections as reasons to question the timing of force.

That case does not prove an eventual agreement was available. It asks whether a narrower interim constraint and renewed inspection access were worth testing before military action, given the risk of a wider war. The competing arguments weigh the risks of waiting with an unverified nuclear stockpile and unresolved enrichment demand against the risks of military action.

The aftermath did not settle the central dispute

Iran launched retaliatory attacks on targets throughout the Middle East and tried to assert control over the Strait of Hormuz, a September 2026 Congressional Research Service report said. The United States and Iran agreed to an April ceasefire and signed a June memorandum to end the conflict, but the memorandum collapsed weeks later amid renewed fighting. As of September 2026, the report said, they were again trading limited strikes.

In reports dated June 4 and September 1, 2026, the IAEA said Iran had not confirmed the status of the affected facilities and associated nuclear material. Destroying or damaging a facility is not the same as accounting for all material or restoring inspectors’ access.

On September 26, Oman’s foreign minister met a U.S. assistant secretary to discuss keeping communication channels open for continued diplomacy.

The timeline shows that the strikes came while the mediator and the United Nations still saw a negotiating process in motion and the White House said diplomacy had failed; it does not establish whether that process would have resolved the dispute, or whether force will.