Aiming to end the war before it began, US forces opened "Operation Iraqi Freedom" with an emphatically personal strike against Saddam Hussein. Naval-based cruise missile attacks joined F-117 stealth fighters in a so-called "decapitation attack" on Hussein's leadership.
But just hours after what President Bush called the "opening stages" of "a broad and concerted campaign," Iraqi leader Saddam Hussein appeared on TV, urging his people to "draw your sword" against the invaders.
Iraqi forces retaliated with missile strikes against US forces in the Kuwaiti desert and the gulf nation's capital. US military officials said one missile was intercepted and the rest fell harmless.
News of the war's start rippled quickly around the globe, intensifying feelings about a conflict that has been center stage long before the first missiles flew.
Russia and China denounced US actions, while France and Germany lamented the strikes and warned of the potential for catastrophe. Dozens of other countries avoided direct denouncements, but expressed regret that the problem could not be solved peacefully through the United Nations.
US missiles struck Baghdad at dawn Thursday, launching a war on Iraq that has no precedent in modern history.
Anti-aircraft fire peppered the sky in response. Reports from eyewitnesses indicated that one target, in the east of the city, had been hit three or four times. A black pall of smoke rose nearby, though it was not entirely clear that the smoke was the result of US strikes.
The first strike of Gulf War II in 2003 was far different from the opening moments of Gulf War 1 in 1991 - and therein lies what US military commanders believe will be the secret of their success.
Where 12 years ago the opening salvo of bombs against Baghdad was fierce, concerted, and part of a long-set plan, the opening moments of George W. Bush's military campaign to oust Saddam Hussein seemed almost anti-climactic. US intelligence indicated an opportunity to lob a few guided weapons at a leadership target - probably Hussein himself - and command authorities took it.
It's these two aspects of the modern US military - its flexibility, and its precision - that the Pentagon believes are its most deadly attributes. That is one big reason why the force amassed to topple Saddam today is far smaller, in terms of manpower, than the one that pushed him out of Kuwait during George Herbert Walker Bush's term.
Eventually the high-tech capability of US weapons will track down the Iraqi leadership and shorten the war, believe US commanders, with far less loss of life on both sides than otherwise might be incurred.
In his address announcing that the Iraqi campaign had begin, President Bush noted on Wednesday night that the US and its allies were only in the "opening stages of what will be a broad campaign".
More concerted strikes will come, Bush implied. He said the war may yet be longer and more difficult than many have anticipated.
"Now that the conflict has begin the only way to limit is duration is to apply decisive force," he said.
Addressing a concern of opponents to his actions around the world, a somber president said that the US would do all it could to limit civilian casualties.
"This will not be a campaign of half measures and we will accept no outcome but victory," he added. "We have no ambition in Iraq but to remove a threat and restore the country to its people."
The war, launched in the teeth of widespread international opposition, will test both new weapons and the US administration's novel doctrine of pre-emptive armed action against its enemies. The President warned that the conflict "could be longer and more difficult than some predict."
So the chapter of diplomacy ended, and that of combat began, while tens of thousands of young American service personnel waited with relief and trepidation for their orders, and the population of Baghdad fled or hid in any secure spot it could find, unsure of the future of itself, and its governing regime.
Material from wire services was used in this report.