Vice President Dick Cheney and Defense Secretary Donald Rumsfeld led the memorial service to honor the 184 people who died five years ago, when terrorists crashed a plane into the Pentagon. Vice President Cheney vowed that America will never appease terrorists, while Secretary Rumsfeld called for national unity to fight extremism.

Vice President Dick Cheney (l) and Defense Secretary Donald Rumsfeld at the Pentagon, September 11, 2006

At a memorial service near the site where American Airlines Flight 77 slammed into the Pentagon five years ago, Vice President Cheney and Secretary Rumsfeld walked side-by-side to the speaker's platform.

A large American flag was draped over part of the building, resembling the flag firefighters unfurled over the wall during rescue efforts, in a patriotic gesture still remembered as a sign of the nation's strength immediately following the attacks.

Cheney told the crowd, which included families who lost loved ones during the attack on the Pentagon, that America has learned difficult lessons since that fateful day.

"We have learned that oceans do not protect us, and threats that gather thousands of miles away can now find us here at home," he said. "We have learned that there is a certain kind of enemy, whose ambitions have no limits and whose cruelty is only fed by the grief of others. In these years, we also found our mission, to defend America against a present danger, and to offer democracy and hope as the alternative to extremism and terror."

The vice president said America has a history of fighting tyranny and will never give in to terrorism.

"This nation has defeated tyrants and liberated death camps, raised the lamp of liberty to every captive land," he said. "We have no intention of ignoring or appeasing history's latest gang of fanatics trying to murder their way to power."

Secretary Rumsfeld, who appeared to struggle with his emotions as he recalled the day of the attacks, said terrorists are failing in their efforts to intimidate Americans.

He called on the nation to honor those who died by supporting members of the military, who are fighting the war on terrorism.

"The highest tribute we can pay to them is to commit ourselves to doing everything possible to fight the extremists wherever they are, to making every effort to stay united as a country and to give our truly outstanding men and women in uniform all that they need to succeed," he said.

Top Pentagon officials say, since September 11, 2001, more than 1.3 million Americans have served in the nation's military in Afghanistan, Iraq and in the Persian Gulf region.

At the Pentagon, construction has begun on a memorial to remember the victims who died five years ago.