As much of the nation was just starting the day on the morning of September 11, 2001, 19 terrorists hijacked four East Coast flights, crashing three of the airplanes into targets in New York and Washington, D.C., with the fourth plane slamming into a field in Pennsylvania after passengers fought back. 

In the end, 2,977 people died, making it the deadliest attack on U.S. soil in history.

The al Qaeda-led attacks prompted President George W. Bush to announce a global “War on Terror” military campaign, in which he called on world leaders to join the U.S. in its response.

“Every nation in every region now has a decision to make,” he said in a national address. “Either you are with us or you are with the terrorists.”

Below is a timeline of notable events.

America Responds to 9/11

• Sept. 11, 2001: Terrorists hijack four U.S. planes, crashing two into the Twin Towers of the World Trade Center in lower Manhattan, while a third hits the U.S. Pentagon minutes later. The fourth plane, targeted to hit the White House, crashes in a field near Shanksville, Pennsylvania, after passengers attacked the terrorists. The death toll, not including the `9 hijackers, was 2,977.

• Sept. 12, 2001: Bush addresses the nation, announcing war and stating: “The United States of America will use all our resources to conquer this enemy. We will rally the world. We will be patient. We’ll be focused, and we will be steadfast in our determination. This battle will take time and resolve, but make no mistake about it, we will win.”

• Sept. 20, 2001: In a speech addressing Congress and the nation, Bush announces the War on Terror, saying, “Our war on terror begins with al Qaeda, but it does not end there. It will not end until every terrorist group of global reach has been found, stopped and defeated.”

• Sept. 25, 2001: Defense Secretary Donald Rumsfeld announces the anti-terror campaign as “Operation Enduring Freedom,” which he says will take years to fight. The following day, Saudi Arabia ends diplomatic ties with Afghanistan’s Taliban government.

War in Afghanistan Begins

• Oct. 7, 2001: Airstrikes by the United States and Great Britain are launched in Afghanistan at Taliban and al Qaeda training camps and targets. “What America is tasting now is only a copy of what we have tasted,” al Qaeda leader Osama bin Laden says in a video statement released the same day. “Our Islamic nation has been tasting the same for more than 80 years of humiliation and disgrace, its sons killed, and their blood spilled, its sanctities desecrated.”

• Oct. 19-20, 2001: The ground war begins, with special forces striking in Kandahar. In the coming weeks, Britain, Turkey, Germany, Italy, The Netherlands, France and Poland all announce they will deploy troops to Afghanistan.

• Nov. 9, 2001: The Afghan Northern Alliance captures Mazar-e-Sharif, a Taliban stronghold. 

Nov. 13, 2001: Kabul falls following airstrikes and ground attacks by the United States and Afghan Northern Alliance.

Dec. 6-17, 2001: The Battle of Tora Bora rages in a cave complex in Eastern Afghanistan’s White Mountains. U.S.-led coalition forces attempt to capture al Qaeda leader Osama bin Laden, but he escapes.

Dec. 7, 2001: Kandahar, the last major stronghold of the Taliban, falls.

• Feb. 21, 2002: A video confirms the execution-style death of Wall Street Journal reporter Daniel Pearl by Khalid Sheikh Mohammed, a self-described mastermind of the 9/11 attacks.

• June 13, 2002: Hamid Karzai, a favored candidate of the U.S., is elected by a traditional Afghan Loya Jirga council to a two-year term as Afghanistan’s transitional head of state. In 2004, he becomes Afghanistan’s first democratically elected president.

Iraq War Begins

• March 19, 2003: U.S. and coalition forces invade Iraq following intelligence that the country and its dictator, Saddam Hussein, possessed or were developing weapons of mass destruction.

May 1, 2003: Bush delivers a speech aboard the aircraft carrier USS Abraham Lincoln proclaiming, “Mission Accomplished,” saying that major combat efforts for the war in Iraq will end. “The battle of Iraq is one victory in a war on terror that began on September the 11th, 2001 and still goes on,” he says.

• Aug. 19, 2003: Twenty-three people, including a top United Nations official, are killed and 100 wounded after a suicide bomber drives a truck into UN headquarters in Baghdad.

Dec 13, 2003: Saddam Hussein is captured by U.S. soldiers in ad-Dawr, Iraq.

• March 11, 2004: A coordinated bombing of four commuter trains in Madrid kills 191 people and injures more than 2000. Islamic militants, based in Spain but inspired by al Qaeda, are later considered the prime suspects.

• July 7, 2005: Terrorist bombings on the London Underground and atop a double-decker bus kill 52 people and injure more than 700. Documents recovered in 2012 will reveal the attacks were planned by a British citizen working for al Qaeda.

Saddam Hussein, Bin Laden Killed

• Dec. 30, 2006: After being sentenced to death by hanging for war crimes and crimes against humanity, Saddam Hussein is executed in Baghdad.

• June 30, 2009: Sgt. Bowe R. Bergdahl walks away from his post in Afghanistan and is kidnapped by the Taliban. Released in 2014, he is later dishonorably discharged.

• Aug. 30, 2010: In an Oval Office address, President Barack Obama declares an end to U.S. combat operations in Iraq.

• May 2, 2011: Osama bin Laden is killed by U.S. special operations forces during a raid at an Abbottabad, Pakistan compound.

• June 22, 2011: In a televised address, Obama announces a withdrawal of U.S. troops from Afghanistan and a hand-over of power to Afghani security by 2014.

• August 2011: Thirty-eight service members are killed when the helicopter they are aboard comes under fire. This month becomes the deadliest ever for U.S. forces in Afghanistan with 66 fatalities.

• Dec. 28, 2014: The War in Afghanistan officially ends, though Obama states 10,800 U.S. troops will remain.

• Jan. 28, 2019: The U.S. and Taliban leaders work toward an agreement for the withdrawal of the 14,000 U.S. troops who remain in Afghanistan.