Iran’s announcement — that its nuclear program “will have no limitations in production, including enrichment capacity” — was among the biggest consequences so far in the chaotic aftermath of the killing in Baghdad of the commander, Maj. Gen. Qassim Suleimani, the country’s de facto No. 2 official.

Iran said it would return to the nuclear limits if American sanctions — which President Trump imposed on the country after withdrawing the U.S. from the nuclear deal in 2018 — were lifted. But amid widespread anger and mourning in Iran, Tehran is widely expected to hit back at American interests, and Mr. Trump has said the U.S. could strike sites in Iran if the country retaliates.

Responses: American allies in the Middle East, fearing they may pay a price for the killing of General Suleimani, have largely kept quiet about it. And the European Union’s foreign policy chief, Josep Borrell, has invited the Iranian foreign minister to Brussels for talks.

What’s next: Prime Minister Adel Abdul Mahdi of Iraq is expected to sign a bill, approved by Parliament on Sunday, that would expel U.S. troops from the country. And a U.S.-led coalition says it’s ending its yearslong mission of attacking the Islamic State and training local forces in Syria and Iraq.

Analysis: Our chief White House correspondent writes that the fallout from the killing will test whether Mr. Trump’s critics — who have long argued that he was too erratic to face moments of crisis — were correct.