• President Joe Biden in an address to the nation Tuesday defended his decision to end the U.S. war in Afghanistan after nearly 20 years of conflict.
• Biden said the U.S. must learn from its mistakes by setting clear goals when it goes to war and not becoming involved in nation building.
• "This decision about Afghanistan is not just about Afghanistan, it's about ending an era of major military operations to remake other countries," Biden said.
• The Taliban, who were ousted from power by the U.S. shortly after the Sept. 11, 2001, terrorist attacks, now control nearly all of Afghanistan.

WASHINGTON — President Joe Biden in an address to the nation Tuesday gave a full-throated defense of his decision to end the U.S. war in Afghanistan after nearly 20 years of conflict, declaring the era of large U.S. military deployments to rebuild other nations as over.

Biden's address came just 11 days before the 20th anniversary of the Sept. 11, 2001, terrorist attacks that precipitated the U.S. intervention in Afghanistan.

"My fellow Americans, the war in Afghanistan is now over," Biden said from the White House.

"I'm the fourth president who has faced the issue of whether and when to end this war," he said.

"When I was running for president I made a commitment that I would end this war, and today I have honored that commitment. It was time to be honest with the American people; we no longer had a clear purpose in an open-ended mission in Afghanistan," he said.

"This decision about Afghanistan is not just about Afghanistan, it's about ending an era of major military operations to remake other countries," the president said.

At 3:29 p.m. ET on Monday, one minute before midnight Kabul time, the last C-17 cargo aircraft carrying U.S. forces took off from Hamid Karzai International Airport, effectively ending America's two-decade military campaign in Afghanistan.

The Taliban, ousted from power by the U.S. shortly after the 9/11 attacks, now control nearly all of the country.

The departure of U.S. forces came at the end of a colossal 17-day humanitarian evacuation of 123,000 people desperate to flee Taliban rule. Of those, 6,000 were U.S. citizens.

In the final days of the mission, a suicide bomber affiliated with ISIS detonated an explosive near the gates of the airport, killing 13 U.S. service members and more than 100 Afghans.

Biden praised the service members who gave their lives as heroes and thanked all members of the military, the diplomatic corps and the intelligence community who risked their safety for what he called a mission of mercy.

On Sunday, the president and first lady Jill Biden traveled to Dover Air Force Base to meet privately with the families of the fallen before observing the dignified transfer of American flag-draped caskets from a C-17 military cargo plane to a vehicle.

"We owe them and their families a debt of gratitude that can never be repaid, but we should never ever forget," the president said of the fallen on Tuesday.

Though Biden said he took full responsibility for the decision to withdraw by Aug. 31, he pushed back against critics who say the White House was unprepared for the chaos that ensued as American forces exited and the Taliban rapidly seized Afghanistan.

The president said he tasked his national security team to prepare for every eventuality, including a swift Taliban takeover, and blamed the Afghan government for the country's rapid collapse.

"We were ready when the Afghan security forces after two decades of fighting for their country and losing thousands of their own did not hold on as long as anyone expected," Biden said.

"We were ready when the people of Afghanistan watched their own government collapse and the president flee amid the corruption and malfeasance, handing over the country to their enemy, the Taliban, and significantly increasing the risk to U.S. personnel and our allies," Biden said.

"Let me be clear, leaving on Aug. 31 is not due to an arbitrary deadline. It was designed to save American lives," the president said.

"It was time to end this war," Biden said. "I was not going to extend this forever war, and I was not extending a forever exit."

Marine Corps Gen. Frank McKenzie, the four-star commander of U.S. Central Command, said no Americans were aboard the final five flights out of Kabul on Monday. Secretary of State Antony Blinken said during a Monday evening address that fewer than 200 Americans are still seeking evacuation.

McKenzie, who oversees the U.S. military mission in the region, added that there were no evacuees left at the airfield when the last C-17 took off. All U.S. service members and Afghan troops who helped defend the airport, along with their families, were also airlifted out on Monday, according to the general.

Biden in his Tuesday address said that "90% of Americans in Afghanistan who wanted to leave were able to leave." The U.S. will hold the Taliban accountable for guaranteeing safe passage to anyone who still wants to leave the country, he said.

"For those remaining Americans, there is no deadline. We remain committed to get them out if they want to come out," the president said.

The U.S. and NATO launched their military campaign in Afghanistan in October 2001, weeks after the 9/11 attacks. The Taliban at the time provided sanctuary to al-Qaeda, the terrorist group that planned and carried out the devastating attacks on the World Trade Center and the Pentagon.

About 2,500 U.S. service members have died in the conflict, which also claimed the lives of more than 100,000 Afghan troops, police personnel and civilians. The wars in Afghanistan, Iraq and Syria have cost U.S. taxpayers more than $1.57 trillion collectively since Sept. 11, 2001, according to a Defense Department report.

Biden, in his address Tuesday, said the U.S. must learn from the mistakes of its two-decade military intervention in Afghanistan. The U.S. achieved its mission to decimate al Qaeda and kill the terrorist group's leader, Osama bin Laden, a decade ago, the president said.

Biden vowed to defend the U.S. against evolving threats from terrorist groups, such as ISIS, without getting the U.S. involved in another ground war. The U.S. must now confront challenges from powerful adversaries such as Russia and China as well, he said.

"As we turn the page on the foreign policy that has guided our nation over the last two decades, we've got to learn from our mistakes," Biden said.

"First, we must set missions with clear achievable goals, not ones we'll never reach. And second, we must stay clearly focused on the fundamental national security interests of America."