WASHINGTON – Taking the nation to war, President Bush said the conflict in Iraq may be long and difficult but the U.S. troops will succeed at their mission “to disarm Iraq, to free its people and to defend the world from grave danger.”

“The people of the United States and our friends and allies will not live at the mercy of an outlaw regime that threatens the peace with weapons of mass murder,” the president said in an Oval Office address a little more than two hours after his 8 p.m. EST ultimatum for Saddam Hussein to give up power.

He said U.S. forces launched airstrikes against “targets of military importance.” A U.S. military official said about three dozen cruise missiles were fired from a small number of ships at “leadership targets.”

The official, who spoke on condition of anonymity, said he was not certain whether Saddam was a target. Shortly before the attack, Bush was told U.S. intelligence believed Saddam was still in Iraq.

“These are opening stages of what will be a broad and concerted campaign,” the president said.

He spoke in vague but grim terms about the sacrifices ahead.

“A campaign on the harsh terrain of a nation as large as California could be longer and more difficult than some predict,” he said.

“America faces an enemy who has no regard for conventions of war or rules of morality.”

There was no indication whether the attack was successful.

“Now that the conflict has come, the only way to limit its duration is to apply decisive force,” the president said. “And I assure you, this will not be a campaign of half measures and we will accept no outcome but victory.”

The strikes used Tomahawk cruise missiles and precision-guided bombs dropped from F-117 Nighthawks, the Air Force’s stealth fighter-bombers, military officials said.

Bush gave the attack go-ahead near the end of a hastily arranged three-and-a-half-hour meeting with his war council – including Defense Secretary Donald H. Rumsfeld and Gen. Richard Myers, chairman of the Joint Chiefs of Staff. It was the third meeting of the day between Bush and the group.

A senior White House official, speaking on condition of anonymity, said that military advisers originally did not intend to begin the assault Wednesday. However, Bush was told in the third meeting that fresh intelligence had prompted military planners to change their recommendation.

The official would not say what the intelligence was but said it prompted Bush to order the strike shortly after 6:30 p.m. EST.

The president then reviewed his address with his chief speechwriter and went to the residence for dinner with Laura Bush. They were in the living room when White House chief of staff Andrew Card called to inform the president that intelligence officials had no information that Saddam had left Iraq.

Bush polished his remarks and headed back to the Oval Office to deliver them to a jittery nation.

Moments before his image was beamed to a worldwide audience, Bush was asked by an aide how he was doing. “I feel great,” Bush said, clenching his fist.

He spoke as a U.S.-led force of 300,000 troops ringed Iraq, ready to launch a ferocious assault to topple the Iraqi dictator and capture any weapons of mass destruction.

The United States has initiated attacks in such places as Grenada and Panama, but war in Iraq would set a new standard for pre-emptive military action.

“On my order, coalition forces have begun targeting selected targets of military importance to undermine Saddam Hussein’s ability to wage war,” the president said. “These are the opening stages of what will be a broad and concerted campaign.”

As he has many times in the run-up to war, Bush declared that the United States has “no ambition in Iraq except to remove a threat. Our forces will be coming home as soon as their work is done.”

White House spokesman Ari Fleischer had announced Bush’s plans to speak on short notice. Fleischer spoke as anti-aircraft fire and explosions were heard across Baghdad after air raid sirens went off at the capital at dawn.

Bush’s speech came at the end of an anxious day of waiting at the White House. Extra security enveloped the executive mansion while aides inside whispered rumors of Iraqi defections and surrenders.

Bush sent Congress formal notice that he had determined “further diplomatic and other peaceful means alone” would not be enough to contain the “threat posed by Iraq.” Bush has contended that Saddam possesses chemical and biological weapons that he could use on his enemies or slip to terrorists.

Offering fresh justification for war, the report said one of the spoils of victory may be information about terror cells in the United States.

“United States government personnel operating in Iraq may discover information through Iraqi government documents and interviews with detained Iraqi officials that would identify individuals currently in the United States and abroad who are linked to terrorist organizations,” the report said.

White House officials said the assertion was mostly speculative.