Explained | Why the US attacked Iran

The United States and Israel launched a joint operation in what was one of the deadliest attacks on Iran in decades to kill supreme leader Ayatollah Ali Khamenei on Saturday.

The strikes came only days after US President Donald Trump said he supported peace and said he preferred dialogue over military action with Iran.

Trump had not given explicit warning of the attack that was to come but had warned in his State of the Union speech last week and had released a video message on Saturday, expressing the objectives of the attack.

Here's why the US joined hands with Israel to attack Iran:

Preventing Iran from producing nuclear weapons

The US president has repeatedly said that Iran can never have nuclear weapons.

​He claimed to have "obliterated" Iran's nuclear program in strikes last June, but added that Tehran was working on rebuilding the programme.

"Just imagine how emboldened this regime would be if they ever had and actually were armed with nuclear weapons as a means to deliver their message," he said on Saturday.

Even in June, the US and and Israel had attacked claiming that Iran was too close to get a nuclear weapon.

Trump on Wednesday said Iran would have become a nuclear power within two weeks had the US not struck three key nuclear sites last ⁠June.

The United Nations' International Atomic Energy Agency (IAEA), however, said that the US intelligence has assessed that Iran shuttered a nuclear weapons development program in 2003 and Tehran denies ever seeking nuclear weapons.

There are also reports that claim Iran has no credible civilian justification for Iran's enrichment of uranium to the levels ⁠it has produced. The IAEA termed this as a serious concern.

No other country has done so without eventually producing nuclear weapons.

Targeting Iran's missile programme

Trump, in his State of the Union speech, had said Iran has advanced in its missile programme, terming it a threat to the US.

On Saturday, he said Iran had attempted "to continue developing long-range missiles that can now threaten our very good friends and allies in Europe, our troops stationed overseas, and could soon reach the American homeland."

Iranian state media has also claimed that the country is developing a missile that can reach the US.

Eliminate Iranian threat to US allies

Another objective Trump mentioned on Saturday was "to defend the American people by eliminating imminent threats from the Iranian regime, a vicious group of very hard, terrible people."

He ‌said Iran's "menacing activities directly endanger the United States, our troops, our bases overseas, and our allies throughout the world."

Trump went back in history, citing the violent takeover of the US Embassy in Tehran in 1979. At that time dozens were held hostages for 444 days; He further referred to an attack by its "proxies" on a US ‌Marine barracks in Beirut in 1983 that killed 241 American military personnel, and "countless" other actions against US forces in the Middle East in recent years, and international shipping lanes.

Trump also highlighted Iran's backing of the Hamas, which launched a deadly cross-border attack on Israel on October 7, 2023.

Treatment of Iranian protesters

Trump, in his State of Union address claimed that Iran had killed 32,000 protesters in the protests through January and February.

On Saturday, he referred to Iran killing "tens of thousands of its own citizens on the street as they protested."

Meanwhile, Iran has claimed much lesser casualties. Iranian Foreign Minister Abbas Araqchi said Tehran had published a "comprehensive list" of all 3,117 killed in the unrest.

Regime change

This is perhaps the biggest objective of the United States. Trump called the people of Iran to rise up and take over power from their rulers.

"I say tonight that the hour of your freedom is at hand. When we are finished, take over your government. It will be yours to take. This ​will be probably your only chance for generations," he said.

Trump was also the first to announce that supreme leader Ayatollah Ali Khamenei was killed in the strikes.

Israeli Prime Minister ​Benjamin Netanyahu had confirmed earlier that Khamenei's compound had been destroyed and a senior Israeli official earlier told Reuters his body had been found.

Iranian state media later confirmed Khamenei had been killed in the attack.