"Today, we've had a national tragedy," he said. "Two airplanes have crashed into the World Trade Center in a terrorist attack on our country."

Bartlett interjected. "We don't know for sure it was a terrorist attack."

"Sure it is," Bush said. "What else do you think it is?"

Fleischer and Scott McClellan, the deputy press secretary, agreed.

"I'm just saying we have not confirmed anything yet," Bartlett said. "We don't know who is responsible."

"Then just say 'apparent' terrorist attack," McClellan said.

On the notepad, Bush wrote that the FBI was working to catch those responsible. "We will punish them," he wrote, then crossed out that line. Instead, he wrote, "Terrorism against Amer will not succeed."

A few minutes later, Bush strode into the school gymnasium filled with students and teachers who did not realize what was happening. He told them about the "apparent" terrorist attack and vowed to "hunt down and find those folks who committed this act," choosing an oddly casual way of describing mass murderers. "Terrorism against our nation will not stand," he added, misreading the notes, which said "will not succeed," and in the process unconsciously echoing words his father had used when Saddam Hussein invaded Kuwait. It was a shaky performance that left advisers worried that he had not been reassuring or commanding enough.

Barely a minute after he was done, Bush headed out the door. Just after 9:30 a.m., his motorcade took off for the airport at what seemed like eighty miles per hour. "We were flying, faster than any motorcade I can remember," recalled the White House photographer, Eric Draper.

A minute later, back in the White House, Secret Service agents burst into Cheney's office. "Mr. Vice President, we've got to leave now," barked Special Agent Jimmy Scott, racing around the desk.

The Secret Service had gotten a report of an airplane heading toward the White House. The agent grabbed Cheney's belt from behind with one hand and his shoulder with another and physically rushed him out of the room. "Doors flew open, Secret Service guys came in, and he vanished," O'Keefe remembered. Oddly, Cheney grabbed a copy of the Economist on the way out, thinking for a moment that he might be taken somewhere for a long wait with nothing to do. Rice and Bolten were left staring at each other in shock.

The agents, bristling with guns and urgency, had maneuvered Cheney into the tunnel beneath the White House by 9:37 a.m., just as the plane smashed into the Pentagon instead. Some concluded later that the hijackers tried to find the White House but from the air could not see it amid taller nearby buildings and struck at the military headquarters instead. If so, it saved Cheney's life because the plane would have hit the White House before the agents got him into the tunnel.

The rest of the White House was evacuated. "Women, take off your heels and run!" agents shouted. Outside the gates, frightened aides were told to take off their White House badges in case there were snipers looking for targets. Not knowing what to do, some simply walked home in a daze. Others, alerted by colleagues, headed two blocks to the offices of Daimler Chrysler, where Tim McBride, a veteran of the first Bush White House, sent his own staff home and ordered sandwiches to create a makeshift White House headquarters for seventy-two dislocated presidential aides.

In the tunnel under the White House, Cheney paused when he came across a television, bench, and telephone. While he waited, word arrived of the crash at the Pentagon.

"Get me the president," he ordered an agent.

Bush was in the car heading to the airport when Rice called to tell him about the Pentagon attack. He arrived at Air Force One at 9:45 a.m., bounded up the stairs, and told his agents to make sure his wife and daughters were safe. Laura Bush, hosted by Ted Kennedy on Capitol Hill to testify on behalf of the education program, had been rushed by her security detail to Secret Service headquarters. Their daughters would not be secured for another hour. Lynne Cheney had been brought to the tunnel outside the bunker, joining her husband.

Bush called Cheney. "Sounds like we have a minor war going on here," Bush said. "I heard about the Pentagon. We're at war." He added, "Somebody's going to pay."

Cheney, standing in the tunnel, told Bush to stay away from Washington until they could determine it was safe. Bush argued, but Cheney, Andy Card, and Edward Marinzel, the lead Secret Service agent traveling with the president, prevailed upon him. Eric Draper, the photographer, could see frustration on Bush's face, but he still tried to pump everyone up. "This is what they pay us for, boys," he said.

Air Force One rocketed into the air at 9:54 a.m. without a destination, the pilots aiming to get as high as possible as quickly as possible. By the time they leveled out, they were at forty-five thousand feet, far above normal cruising altitude. Bush, his coat now off, emerged from his cabin. "I just heard Angel is the next target," he said, using the code name for Air Force One. Bush could feel the plane bank sharply to the west and away from Washington.

CHENEY HEADED INTO the bunker three stories under the East Wing, a pair of massive steel doors closing behind him with a loud hiss, forming an airtight seal. Officially known as the Presidential Emergency Operations Center, the bunker was first built in 1934 along with the East Wing; Franklin Roosevelt converted it into an air raid shelter in 1942 during World War II. It was equipped with secure telephones, kept in drawers under the conference table, that looked as if they were from the 1960s, two television screens embedded in the back wall and another couple on a side wall, several bunks for sleeping, and days' worth of food and supplies. But it had never been used in an actual crisis and was "shockingly low-tech," as Joshua Bolten put it.

At some point shortly after stepping into the bunker, Cheney said he talked with Bush again about fighter jets being scrambled to protect Washington. Both he and Bush recalled the vice president asking for authority to shoot down hijacked airliners if they did not follow instructions. "You bet," Bush recalled answering. Rice on the ground and Karl Rove in the air recalled overhearing a call like that, and a military aide remembered Cheney calling Bush shortly after entering the bunker. But none of about a dozen sets of logs and notes kept that day recorded the call, leading some to wonder later whether Cheney did get permission before deciding what to do about further attacks.

When a military aide reported that United Airlines Flight 93 was eighty miles away and heading toward Washington, he asked Cheney whether it should be shot down. In "the time it takes a batter to decide to swing," as Scooter Libby put it, Cheney said yes.

When the plane was believed to be sixty miles away, the aide asked again.

Cheney repeated the order.

Finally, the aide came back a third time.

"Just confirming, sir. Authority to engage?"

"I said yes," Cheney replied, his voice betraying irritation.

Silence came over the room as the gravity of the moment sank in. The vice president had just ordered military warplanes to shoot down a commercial airliner with scores of innocent passengers on board.

Cheney never flinched. "I don't want it to sound heartless, but there was no alternative," he explained later. "It wasn't the kind of thing you agonized over." Thousands of lives were at stake.

On the other side of the table, Bolten, who had not heard any earlier conversation with Bush about shoot-down authority, quietly suggested the vice president call the president to inform him about the order. That call was logged at 10:18 a.m., and Bush ratified the vice president's decision. Bolten later said he was not questioning whether Cheney had permission to give the order but merely thought the president would want to know it had been issued.

A few minutes later, a report came back that United Airlines Flight 93 had crashed. Cheney wondered whether he had just shot down a civilian plane.

In fact, the United jet had gone down in Shanksville, Pennsylvania, at 10:03 a.m., before any order was given. Passengers had staged a revolt. No one knew that yet, but it occurred to Cheney that maybe it was not his shoot-down order that brought down the plane. "I think an act of heroism just took place on that plane," he said to no one in particular.

But he was frustrated not to get a precise report. "You must know whether or not we engaged, whether or not a fighter engaged a civilian aircraft," Cheney said into the phone to the Pentagon. "You have to know the answer to that."

As it turned out, in the confusion of the day, Cheney's order never got passed along to the pilots in the air. F-16 fighters scrambled out of Andrews Air Force Base so quickly they had no missiles. The pilots resolved that if they did receive orders to stop a hijacked plane, they would ram their jets into the target. One of the pilots, Lieutenant Heather Penney, was prepared to do it even knowing that her father, a United Airlines pilot, might be on board.

Cheney looked up to see his deputy national security adviser, Eric Edelman. "Mr. Vice President," Edelman said, "Steve Hadley asked me to come down here." Hadley and Richard Clarke thought Cheney should be evacuated to a remote site in case the White House was still a target.

Cheney, who had been telling Bush to stay away, refused to go himself. "You know, I have got communications with the president here and I have been on the phone with him and this place was meant to be able to operate in a nuclear environment. And if I leave now and go off to one of these other sites, with my helicopters, it will be forty-five minutes before we get on the ground and reestablish contact. There is just too much going on right now. We don't understand the full dimensions of this. So I am staying here. Convey that back to Hadley and Clarke."

Edelman turned around and started to leave.

"Where are you going?" Cheney called after him.

"Well, sir, I am going to carry out your instruction," Edelman said.

"No, I need you here," he said. "Call Hadley."

So Edelman got Hadley on the phone and told him the vice president was staying. Cheney tried to join the secure videoconference Clarke was running out of the Situation Room, but the audio was impossible to make out.

Cheney was exasperated. "Get that off the screen," he finally ordered. "Put up CNN so I can actually find out what is going on around here."

He told Edelman to get on the phone and monitor the Situation Room conference call. But after trying to listen for a while, Edelman finally gave up.

"This is like listening to Alvin and the Chipmunks in the bottom of a swimming pool," he fumed.

Screw it, Cheney said. Get off the phone.

By this point the south tower had collapsed. At 10:28 a.m., Cheney looked up to see the north tower crumble in a smoky heap. Everyone in the room gasped, shock etched on their faces-all except for Cheney, who stared stoically at the television.

Just then came a report of another plane heading to Washington.

"Take it out," Cheney ordered. "If it looks threatening, take it out."

In the end, it turned out to be a medevac helicopter.

Cheney worked with Norman Mineta, the transportation secretary, to ground the four thousand planes in American airspace. Among them was one carrying the president's parents, forced to put down in Milwaukee. With three separate pads of paper in front of him, Cheney kept track of how many planes were still in the air as Mineta called out tail numbers. Other erroneous reports arrived of a bomb at the State Department, a fire on the Mall, airplanes heading toward Camp David and the Crawford ranch, and so forth. Falling back on his continuity-of-government exercises, Cheney ordered officials to find congressional leaders and fly them to a prearranged secure location.

At 10:39 a.m., Cheney got hold of Donald Rumsfeld, who had rushed outside to help with victims when the Pentagon was hit. Cheney updated him.

"There's been at least three instances here where we've had reports of aircraft approaching Washington-a couple were confirmed hijack," Cheney told him. "And pursuant to the president's instructions, I gave authorization for them to be taken out."

The vice president was not sure Rumsfeld was still there. "Hello?"

"Yes, I understand," Rumsfeld said. "Who did you give that direction to?"

"It was passed from here through the center at the White House."

"Okay," Rumsfeld said. "Let me ask the question here. Has that directive been transmitted to the aircraft?"

"Yes, it has," Cheney said.

"So we've got a couple of aircraft up there that have those instructions at this present time?" Rumsfeld asked.

"That is correct. And it's my understanding they've already taken a couple of aircraft out."

"We can't confirm that," Rumsfeld said. "We're told that one aircraft is down but we do not have a pilot report that did it."

Rumsfeld ordered the nation's defense readiness condition elevated to DefCon 3, the highest since the Yom Kippur War of 1973. But several members of the Bush team realized they should make sure the heightened alert status did not alarm the Russians. Rumsfeld, Rice, and Richard Armitage, the deputy secretary of state, all talked with Russian officials, who, as it happened, were conducting military exercises. Vladimir Putin would later make much of being the first foreign leader to call Bush on the day of the attacks to offer support, although he did not initially get through to the president. Rice took the call. "We have canceled our exercises," he told her.

AIR FORCE ONE raced west at full throttle, hitting 630 miles per hour, surprising even some of its crew who did not know it could go that fast. Bush was sobered to look out the window on the left side and see F-16 fighters escorting him, so close he could spot the stubble on the chin of one of the pilots, who saluted him.

The plane headed to Barksdale Air Force Base in Louisiana. It was an aggravating flight. Without its own television stream, the plane picked up feeds from local stations as it flew over various cities and then lost them again. Phone calls got cut off. But Bush saw one of the towers fall and thought to himself that no American president had ever seen so many of his people die all at once before. Three thousand had been killed in the deadliest sneak attack in American history, all on his watch. At the time, he thought it was even more.

The plane landed at Barksdale about 11:45 a.m. East Coast time, and Bush was further taken aback to see the base filled with armed bombers and guarded by rifle-toting troops. "It was surreal," he remembered later. "It was like flying in the midst of a combat zone." With no motorcade waiting for him, Bush climbed into a military vehicle that drove off at great speed.

"Slow down, son," Bush called out. "There are no terrorists on this base."

Bush taped another statement to be played to the nation and called Rumsfeld. "The ball will be in your court," Bush told him.

But the statement was no more reassuring than the earlier one. David Frum, the speechwriter, thought Bush "looked and sounded like the hunted, not the hunter." The communications at Barksdale were inadequate, so at Cheney's suggestion Bush took off again for Offutt Air Force Base in Nebraska, headquarters of Strategic Command, or Stratcom, which was equipped to run a war if need be. On the plane, Bush kept up a running argument over returning. "We need to get back to Washington," he told his Secret Service agent. "We don't need some tinhorn terrorist to scare us off. The American people want to know where their dang president is."

He also grilled Michael Morell, his CIA briefer.

"Who do you think did this?" Bush asked.

"There are two terror states capable, Iran and Iraq, but both have everything to lose and nothing to gain," Morell said. "If I had to guess I'd put a lot of money on the table that it was al-Qaeda."

"So when will we know?"

"We could know it soon, or it could take a while."

Barksdale was not the only place with communications problems. The White House bunker was supposed to have an open phone line with the Situation Room upstairs, but it kept cutting out. Richard Clarke in the Situation Room kept calling back asking for Major Mike Fenzel. The person answering the phone just grunted and passed the phone.

"Who is the asshole answering the phone for you, Mike?" Clarke asked.

"That would be the vice president, Dick," Fenzel said.

While the working assumption was that Osama bin Laden's al-Qaeda was behind the attacks, it did not take long for Iraq to come up. During a meeting at the Pentagon at 2:40 p.m., just five hours after the building was hit, Rumsfeld broached the idea of attacking Saddam Hussein, even though there was no evidence of his involvement. Stephen Cambone, a Rumsfeld aide, scribbled notes, using abbreviations for Hussein and bin Laden: "Best info fast. Judge whether good enough hit S.H. @ same time-Not only UBL."

At the White House, the air in the bunker had grown stale and heavy with carbon dioxide. Secret Service agents tried to clear space around Cheney. David Addington asked nonessential people to leave. Cheney had grown concerned that the president's brief statements were not enough to let Americans know that their government was operating. He was loath to make a public appearance himself, knowing it would fuel the impression that he was really running the show. "We were at war," he said later. "Our commander in chief needed to be seen as in charge, strong, and resolute-as George W. Bush was. My speaking publicly would not serve that cause." So he assigned Karen Hughes to conduct a briefing.

He wanted to make sure she had the best information when she did. By now, he knew just one plane had gone down, but he was still unsure whether it was because of his order.

"Call the NMCC," Cheney told his aide Eric Edelman, referring to the National Military Command Center, "and make sure we didn't shoot that plane down. We only get one chance to have the first take on the story, and if we get it wrong, we'll pay an enormous price. So make sure we didn't shoot it down."

Edelman made the call. The military staff at the center said no, there was no contact between air force fighters and the plane that went down in Pennsylvania.

Edelman reported back.

"Go ask them again," Cheney instructed.

"But, sir, I just asked them."

"Go ask them to check again."

Edelman got back on the phone and asked the military center to double-check. No, came the response, we had nothing to do with it. Edelman reported back to Cheney again.

Still unsatisfied, Cheney said, "I want you to go make sure."

Edelman made a third call and for the third time came back with the same answer.

Only then was Cheney satisfied.

BUSH LANDED AT Offutt at 2:50 p.m. East Coast time and headed into a command center like the one in the movie WarGames. At 3:15 p.m., the president convened a secure videoconference with top advisers. Appearing on separate video feeds were Cheney, Rumsfeld, George Tenet, and Robert Mueller, who had been FBI director for just a week.

"We're at war," Bush began. "We will find these people and they will suffer the consequence of taking on this nation. We will do what it takes."

Tenet told him it did indeed look as if al-Qaeda were responsible. A check of the manifests of the four hijacked planes had found three passengers who were known members, and electronic surveillance had picked up congratulatory communications among al-Qaeda figures.

Even as they discussed the response, a voice interrupted the videoconference to announce that a plane from Madrid was not responding to radio calls; permission to shoot it down was requested. When is this going to end? Bush thought. He authorized lethal action if necessary. Soon the voice interrupted again to report that the Madrid flight had landed in Lisbon.

Bush understood it was not going to end and that his presidency as he knew it was over. "We are at war against terror," he declared. "From this day forward, this is the new priority of our administration."

After the conference, he ordered his plane back to Washington so he could address the nation from the Oval Office. "If I'm in the White House and there's a plane coming my way, all I can say is I hope I read my Bible that day," he said.

Before taking off, he called Theodore Olson, the lawyer who had handled Bush v. Gore and later became his solicitor general. Olson's wife, Barbara, a lawyer and well-known political figure in Washington, had been on the plane that hit the Pentagon. Bush promised Olson he would find the people responsible.

After landing at Andrews Air Force Base, Bush boarded his marine helicopter to fly the last few miles to the White House. As it banked over Washington, he saw the plumes of smoke still emerging from the Pentagon. "The mightiest building in the world is on fire," he muttered. "That's the twenty-first-century war you just witnessed."

Marine One touched down at 6:55 p.m. on the South Lawn, where picnic tables and chuckwagons had been set up only that morning for a congressional picnic that was to be held that evening. Bush met with aides for a few minutes and then headed to the bunker, which he had never visited before. He found Laura waiting for him and hugged her, then caught up with Cheney.

At 8:30 p.m., Bush sat at his desk in the Oval Office as cameras transmitted his first extensive remarks on the crisis. The speechwriters had hashed through multiple drafts, but in the end Hughes put her pen through most of it. Bush did not declare war that night, because he wanted to reassure Americans, and he uttered lines that made the speechwriters cringe, such as "These acts shattered steel but they cannot dent the steel of American resolve." The speechwriters called it the "Awful Office Address." Michael Gerson, who had been stuck in highway traffic near the Pentagon when the hijacked plane hurtled into the building, thought it was "unequal to the moment" and made Bush look "stiff and small."

But one line from the speechwriter Matthew Scully survived: "We will make no distinction between the terrorists who committed these acts and those who harbored them."

Just like that, Bush declared a sweeping new doctrine in American security, one that he had not discussed in advance with Cheney, Rice, Rumsfeld, or Colin Powell. This would not be "pounding sand," as he often characterized what he saw as Bill Clinton's feckless responses to terrorist attacks of the past. This would be going after anyone and any nation that had anything to do with it, including Afghanistan, where al-Qaeda had bases, and possibly even Iraq, which was a designated state sponsor of terrorism.