In attacking Iran and killing the regime's supreme leader, US President Donald Trump has made an enormous bet: that he can succeed where past presidents have failed by using American military force to reshape the Middle East.
Trump will claim a generational victory if the US succeeds in fully destroying Iran's nuclear programme and bringing about regime change in Tehran using air power alone, even if there seems to be no clear plan from Washington for what would come after the Islamic Republic.
But if the military strike, called Operation Epic Fury by the Pentagon, fails, or sparks a wider regional conflagration that demands ongoing US involvement, Trump could hurt his legacy as well as Republicans' chances to retain control of Congress in the November midterm elections.
The president signalled how much is at stake in remarks early on Saturday when he announced the start of a military campaign in Iran.
"American heroes may be lost", Trump said. He argued this would be a necessary price to pay to inflict damage on a regime he said has sown chaos across the Middle East since seizing power in 1979.
