Two al-Qaeda attackers assassinate Ahmad Shah Massoud, a pivotal Afghan resistance leader, two days before the September 11th attacks in the United States.

Al-Qaeda, is a pan-Islamist militant organization led by Sunni jihadists who self-identify as a vanguard spearheading a global Islamist revolution to unite the Muslim world under a supra-national Islamic caliphate. Its membership is mostly composed of Arabs but also includes people from other ethnic groups. Al-Qaeda has mounted attacks on civilian, economic and military targets of the U.S. and its allies; such as the 1998 US embassy bombings, the USS Cole bombing, and the September 11 attacks.

On 9 September 2001, Ahmad Shah Massoud was assassinated by two al-Qaeda operatives posing as journalists in Khwaja Bahauddin District, Takhar Province, Afghanistan.

The Northern Alliance, officially known as the United National Front for the Salvation of Afghanistan, was a military alliance of groups that operated between early 1992 and 2001 following the dissolution of the Soviet Union. It was formed by government defectors such as Ahmad Shah Massoud, Burhanuddin Rabbani, Rashid Dostum, Abdul Momim and Ali Mazari. It consisted mainly of ethnicities from northern Afghanistan, such as Tajiks, Uzbeks, Hazaras, and Turkmens, as opposed to the Taliban. At that time, many non-Pashtun Northerners originally with the Republic of Afghanistan led by Mohammad Najibullah became disaffected with Pashtun Khalqist Afghan Army officers holding control over non-Pashtun militias in the North. The alliance's capture of Mazar-i-Sharif and more importantly the supplies kept there crippled the Afghan military and began the end of Najibullah's government. Following the collapse of Najibullah's government, the Alliance would fall with a second civil war breaking out. However, following the Islamic Emirate of Afghanistan's (Taliban) takeover of Kabul, the United Front was reassembled.

The September 11 attacks, also known as 9/11, were four coordinated Islamist terrorist suicide attacks by al-Qaeda against the United States in 2001. Nineteen terrorists hijacked four commercial airliners, crashing the first two into the Twin Towers of the World Trade Center in New York City and the third into the Pentagon in Arlington County, Virginia. The fourth plane crashed in a rural Pennsylvania field during a passenger revolt. The attacks killed 2,977 people, making it the deadliest terrorist attack in history. In response to the attacks, the United States waged the global war on terror over multiple decades to eliminate hostile groups deemed terrorist organizations, as well as the governments purported to support them.