Short answers, pulled from the story.
The Afghan conflict is traced to the 1973 coup that overthrew King Mohammad Zahir Shah, ending his 40-year reign and replacing the Kingdom of Afghanistan with the Republic of Afghanistan under Mohammad Daoud Khan. Full-scale fighting did not erupt until the 1978 Saur Revolution, when the People's Democratic Party of Afghanistan violently overthrew Khan's government.
Operation Cyclone was a joint covert effort by Pakistan, the United States, and Saudi Arabia to arm and fund the anti-Soviet Afghan mujahideen during the Soviet-Afghan War of 1979-1989. The United Kingdom, China, and Iran also contributed support to the mujahideen during this period.
Adding estimates across the individual conflicts, between 1,405,111 and 2,084,468 people had been killed by 2014. The death toll from the Soviet-Afghan War alone has been described as a genocide by a number of sources, with up to 2 million Afghans killed. A total of 14,453 Soviet soldiers also died during the Soviet-Afghan War.
Ahmad Shah Massoud was a mujahideen commander who became the primary leader of the Northern Alliance resistance against the Taliban. He defeated Soviet forces nine times in the Panjshir Valley, warned the European Parliament about an imminent large-scale attack on U.S. soil, and was assassinated on the 9th of September 2001, two days before the September 11 attacks. The Wall Street Journal named him 'the Afghan who won the Cold War.'
The Doha Agreement was a 2020 deal between the Trump Administration and the Taliban providing for a full U.S. withdrawal from Afghanistan in exchange for Taliban pledges not to allow al-Qaeda to re-establish itself and to enter talks with the Afghan government. The agreement required the Afghan government to release 5,000 Taliban prisoners, and was followed by a 70% increase in Taliban attacks on Afghan government forces in the 45-day period after signing.
After President Biden announced a withdrawal deadline of the 31st of August 2021, the Taliban rapidly seized the countryside and then regional capitals. By the 15th of August 2021, the Taliban had encircled Kabul; President Ashraf Ghani fled to Tajikistan, and Kabul fell the same day. Coalition forces destroyed 75 aircraft and over 100 vehicles at the Hamid Karzai International Airport before departing on the 30th of August.