Festivities were first organized last year, when the authorities and Taliban supporters marked the first anniversary of the withdrawal. Taliban fighters held a rally on Massoud Square in Kabul outside the former US embassy building. 
The last American soldier, US Army Major General Chris Donahue, boarded a military transport plane shortly before the deadline for the withdrawal expired on August 31, 2021, ending the grueling 20-year campaign. 
The US and its allies sent troops to Afghanistan in 2001 to fight Al-Qaeda and other jihadist groups as part of Washington’s global ‘War on Terror’ that was proclaimed following the 9/11 terrorist attacks.
The Western forces quickly took Kabul, but the Taliban remained active in large swaths of the country, and the war with insurgents dragged on for many years, while the campaign became more unpopular in the US.
The Taliban eventually recaptured several provincial capitals and seized Kabul with little to no resistance in August 2021. The unexpected fall of the city forced the Pentagon to carry out a hasty evacuation of diplomats, American nationals, and their Afghan helpers.
Washington has been roundly criticized for its handling of the evacuation, and for leaving thousands of allied Afghans behind.