When President Bush announced to the American public Wednesday night at 10:15 his orders to begin military action against Iraq, those orders had been in motion for three hours, flashing through a chain of command that ended at the GIs aboard the six U.S. Navy warships who fired 36 Tomahawk cruise missiles into Baghdad.

How does that happen?

Hours of National Security Council and war cabinet meetings led to the moment. The night before, the president had satisfied the only formal paperwork required by Congress to start the war when he sent a seven-page report to the House speaker and the Senate president pro tempore, stating that diplomatic efforts had failed and military force was required to continue the fight against terrorism.

"That's all he had to do under the war powers resolution," says Roger Davidson, professor emeritus of government and politics at the University of Maryland.

The War Powers Act of 1973 and two congressional authorizations giving the president authority to pursue Sept. 11, 2001, criminals and those who aided them imposed specific reporting requirements on the administration if it used military force. Besides requiring the president to report to Congress "prior to the exercise of such force, . . . but no later than 48 hours after," the most recent authorization, passed in October, also requires him to report every 60 days during the fighting so Congress can review the continuing use of force.

But those reports are technicalities, "like filing your tax returns," according to historian Douglas Brinkley at the University of New Orleans, who says that despite the Constitution seemingly delegating war powers to Congress, "presidents have every right to go to war when they feel national security is at risk."

Loyola Marymount University political scientist Michael Genovese says presidents have increasingly taken command of war powers -- from Truman's police action in Korea and Johnson and Nixon's escalation of the war in Vietnam to military interventions in Panama, Grenada and Kosovo. The United States hasn't formally declared war since 1941 in World War II.

Article I, Section 8, of the Constitution empowers only Congress to declare war, but modern warfare technology requires a faster response to threats and has modified war-making powers -- basically granting the president practical power to act and Congress power to approve.

The "let's roll" moment in Operation Iraqi Freedom occurred at 6:30 p.m. EST Wednesday when the president, as commander in chief, signed the order to strike and issued it to Secretary of Defense Donald Rumsfeld, who was in the Oval Office. Together, the two constitute the National Command Authority that is empowered to command all U.S. combat forces.

The secretary of defense relays the orders to the combatant commander, who, in this military action, is U.S. Central Command's Army Gen. Tommy R. Franks, at his Qatar headquarters.

"Once Franks has it, it goes to his 'targeting cell,' which is a whole bunch of people at USCENTCOM headquarters who decide which weapons will be used to hit what target," says Ivo Daalder, a senior fellow and foreign policy specialist at the Brookings Institution.

The target of the first strike was the building where intelligence sources determined senior Iraqi officials were gathered. The targeting cell decided which weapons would work best before the Iraqi officials left. Their decision: 36 satellite-guided Tomahawk cruise missiles fired from Navy warships.

"They communicated that to the commanders of those ships or squadrons, who then communicated it to the actual pilots," says Daalder. "For the cruise-missile carriers, the specific orders were transmitted to the commander of the fleet, or to the captains of the ships directly, and then to the shooters."

Two to 2 1/2 hours after the president gave the orders to strike Baghdad, GIs pulled the trigger to launch the cruise missiles, which hit their target 30 to 60 minutes later. Within a half-hour of the strike, the president told the American people military strikes had begun.