There is widespread agreement by many commentators both that Donald Trump’s war on the Islamic Republic of Iran, which lasted from 28 February to 17 June 2026, was illegal and also that he lost.

Why it was illegal

It was illegal under US law. Many legal and military experts have said that US actions in Iran are a type that require congressional authorization.

It was illegal under International Law. It violates the UN Charter’s prohibition on the use of force, because the attacks fail to meet the criteria for self-defense and lack authorization from the United Nations Security Council

Why we say Trump lost

There is widespread agreement on this. For example, on 18 June a member of the US House Foreign Affairs Committee, Congresswoman Sydney Kamlager-Dove, wrote the following. By the “deal” she is referring to the Memorandum of Understanding.

“Donald Trump’s arrogance and ignorance led to one of the worst foreign policy decisions of my lifetime. Make no mistake: Trump lost this war. He was so desperate to get out of his own disastrous, illegal war that he got played by the Iranians. He just took an abomination of a “deal” that gives over $300 billion to Iran and lifts sanctions in exchange for a pinky promise that they won’t develop nuclear weapons and will keep the Strait of Hormuz open free of tolls for 60 days.

“What are we left with? 13 brave American servicemembers dead. An estimated $100 billion in tax dollars wasted. Allies are less trusting of our word, and our assets in the region are depleted. The radical, repressive Iranian regime still has the same military and nuclear capabilities that it started with, and is now further emboldened, entrenched, and enriched. Meanwhile, Americans are still suffering from rising prices for gas, food, housing, and health care. Where is the reconstruction plan for the American people?

“Trump never should have gotten us into this deranged war. He never should have torn up President Obama’s Iran deal. And he should have made the case to Congress and the American people as to why we should go war. While I’m grateful that the fighting may cease and our troops will no longer suffer from Trump and Hegseth’s incompetence, it’s clear that Trump was more worried about his poll numbers than protecting American interests.”

So why did he start it and why did is stop it?

He started it because his success in catching the Venezuelan president Nicolás Maduro and his wife made him think he could do the same in Iran. His ignorance of military operations and his incompetence made he think it would be easy.

He stopped it because, as Wikipedia summarised it, Iran’s closure of the Strait of Hormuz, which Trump has never even thought about before he started the war, has already caused the largest-ever monthly increase in oil prices and the largest disruption to world energy supply since the 1970s energy crisis as well as the largest in the history of the world oil market. Other commodity markets to suffer supply disruption and price increases due to the crisis include aluminum, fertilizer and helium.

The Guardian reports that the European Central Bank has already raised interest rates for the first time since 2023 in response to higher inflation caused by Trumps war in Iran.

He knew that, if Iran kept the Strait closed for much longer, the United States would join the rest of the world in entering recession and he would pay at the midterm US elections in November.