2021 Taliban offensive

The Taliban insurgent group and allied militants conducted a military offensive in 2021 that led to the fall of the Islamic Republic of Afghanistan and the end of the nearly 20-year war in Afghanistan that had begun following the United States invasion of the country. The Taliban victory had widespread domestic and international ramifications regarding human rights and proliferation of terrorism. The offensive included a continuation of the bottom-up succession of negotiated or paid surrenders to the Taliban from the village level upwards that started following the February 2020 US–Taliban deal.

The offensive began on 1 May 2021, coinciding with the withdrawal of the United States's 2,500 troops in Afghanistan, and those belonging to other international allies. Large numbers of armed civilians, including women, volunteered with the Afghan Army in defense, while some former warlords, notably Ismail Khan, were also recruited. Despite this, the Taliban managed to make significant territorial gains in the countryside, increasing the number of districts it controlled from 73 to 223 in the first three months of the offensive. On 6 August, the Taliban launched an assault on the provincial capitals, with most of the towns surrendering without a fight, culminating with victories in weeks-long battles of major cities Herat, Kandahar and Lashkargah on 13 August. On 15 August, President Ashraf Ghani fled the country and the Taliban captured the Afghan capital Kabul with only sporadic resistance; thus, the Islamic Republic of Afghanistan's government fell, resulting in the de facto takeover of the country and the reinstatement of the Islamic Emirate of Afghanistan. The speed of the Taliban's takeover came as a surprise to many, including the governments of the United States and their allies, Russia and the Taliban themselves.

Factors prior to May 2021 included the Taliban's effective use of online social media, its strategic choice of attacking northern provinces, and the Taliban's freedom of movement on the main Afghan highways that resulted from the Afghan National Security Forces (ANSF) following the US-recommended strategy of sacrificing rural areas in favour of defending key urban centres.