U.S. AND ISRAEL BEGIN "MAJOR COMBAT OPERATIONS" IN IRAN

Driving the news: In a video statement, Trump accused Iran of conducting "mass terror" ever since the 1979 Islamic Revolution, and declared "we're not going to put up with it any longer."

• "We're going to destroy their missiles and raze their missile industry to the ground. ... We're going to annihilate their navy, we're going to ensure that the region's terrorist proxies can no longer destabilize the region or the world and attack our forces," Trump said. "And we will ensure that Iran does not obtain a nuclear weapon."
• Trump acknowledged the risk of significant American casualties if Iran retaliates. "My administration has taken every possible step to minimize the risk to U.S. personnel in the region," he said.
• He encouraged the people of Iran to remain in their homes during the bombing and "when we are finished, take over your government, it will be yours to take. This will be probably your only chance for generations."

State of play: The first strike on Saturday morning local time appeared to be near the offices of Supreme Leader Ali Khamenei, AP reported.

• Directly targeting Khamenei was among the list of military options Trump reviewed, as Axios previously reported. There's been no confirmation that the strike was aimed at the 86-year-old ayatollah.
• Meanwhile, Israel's military warned the population to prepare for incoming missiles as Iran's retaliation begins.

How it happened: Trump threatened to punish the regime earlier this year if it cracked down during mass protests. After thousands of protesters were killed, Trump nearly ordered strikes in January before delaying his decision.

• He then sent his envoys Steve Witkoff and Jared Kushner to hold multiple rounds of nuclear negotiations with Iran, while simultaneously launching one of the biggest U.S military buildups in recent history. It includes two aircraft carriers and hundreds of warplanes and missiles.
• Both sides described the most recent round of nuclear talks on Feb. 26 as successful, though no agreement was reached.
• In his statement, Trump said his administration had "sought repeatedly" to make a nuclear deal, but Iran had "refused."
• Trump has made misleading comments about the state of Iran's nuclear and missiles programs in the lead-up to the strikes, describing a more urgent security threat to the U.S. than available evidence demonstrates.

Behind the scenes: Several of Trump's top advisers, including Joint Chiefs Chair Gen. Dan Caine, had privately warned him about the risk of becoming entangled in a prolonged conflict.

• Some Persian Gulf leaders are deeply concerned that Iran will retaliate by attacking their countries, several of which host U.S. military bases.
• Israel has been advocating for a renewed operation against Iran, along with a few hawkish members of Trump's circle, like Sen. Lindsey Graham (R-S.C.).
• Trump has repeatedly said he would prefer a deal, but he'd turn to military force if he couldn't get one.

Catch up quick: Trump has assembled a massive military force off of Iran, including two aircraft carrier strike groups and hundreds of aircraft and Tomahawk missiles.

• U.S. and Israeli officials have told Axios that any operation would likely be much larger in scale than last June, when the U.S. struck three Iranian nuclear facilities before seeking a truce. Trump claims those facilities were destroyed.

State of play: Explosions were reported in other Iranian cities beyond Tehran.

• A state media outlet linked to the Islamic Revolutionary Guard Corps said Tehran was preparing a "crushing response."
• Israeli Prime Minister Benjamin Netanyahu released a statement saying the objective of the operation was "to remove the existential threat posed by the terrorist regime in Iran."

Go deeper: What to know about Ali Khamenei, Iran's supreme leader

Editor's note: This article has been updated with more details on the strikes.