War in Afghanistan (2001–2021)

Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central and South Asia. It is bordered by Pakistan to the east and south, Iran to the west, Turkmenistan to the northwest, Uzbekistan to the north, Tajikistan to the northeast, and China to the northeast and east. Occupying 652,864 square kilometers (252,072 sq mi) of land, the country is predominantly mountainous with plains in the north and the southwest, which are separated by the Hindu Kush mountain range. Kabul is the country's capital and largest city. Afghanistan's population is estimated to be between 40 and 50 million.

Human habitation in Afghanistan dates to the Middle Paleolithic era. Popularly referred to as the graveyard of empires, the land has witnessed numerous military campaigns, including those by the Persians, Alexander the Great, the Maurya Empire, Arab Muslims, the Mongols, the British, the Soviet Union, and a US-led coalition. Afghanistan also served as the source from which the Greco-Bactrians and the Mughals, among others, rose to form major empires. Because of the various conquests and periods in both the Iranian and Indian cultural spheres, the area was a center for Zoroastrianism, Buddhism, Hinduism, and later Islam. The modern state of Afghanistan began with the Durrani Afghan Empire in the 18th century, although Dost Mohammad Khan is sometimes considered to be the founder of the first modern Afghan state. Afghanistan became a buffer state in the Great Game between the British Empire and the Russian Empire. From India, the British attempted to subjugate Afghanistan but were repelled in the First Anglo-Afghan War; the Second Anglo-Afghan War saw a British victory. Following the Third Anglo-Afghan War in 1919, Afghanistan became free of foreign political hegemony, and emerged as the independent Kingdom of Afghanistan in 1926. This monarchy lasted almost half a century, until Zahir Shah was overthrown in 1973, following which the Republic of Afghanistan was established.

Combatant is the legal status of a person entitled to directly participate in hostilities during an armed conflict, and may be intentionally targeted by an adverse party for their participation in the armed conflict. Combatants are not afforded immunity from being directly targeted in situations of armed conflict and can be attacked regardless of the specific circumstances simply due to their status, so as to deprive their side of their support.

In an interstate conflict, the definition of "combatant" is found in Article 43 (2) of Additional Protocol I to the 1949 Geneva Conventions: "Members of the armed forces of a Party to a conflict (other than medical personnel and chaplains covered by Article 33 of the Third [Geneva] Convention) are combatants, that is to say, they have the right to participate directly in hostilities." Combatants when captured by an opposing party are automatically granted the status of protected persons, whether as prisoners of war or unlawful combatants.

Modern warfare is warfare that diverges notably from previous military concepts, methods, and technology, emphasizing how combatants must modernize to preserve their battle worthiness. As such, it is an evolving subject, seen differently in different times and places. In its narrowest sense, it is merely a synonym for contemporary warfare.

In its widest sense, it includes all warfare since the "gunpowder revolution" that marks the start of early modern warfare, but other landmark military developments have been used instead, including the emphasis of artillery marked by the Crimean War, the military reliance on railways beginning with the American Civil War, the launch of the first dreadnought in 1905, or the use of the machine gun, aircraft, tank, or radio in World War I.

The history of Afghanistan covers the development of Afghanistan from ancient times to the establishment of the Emirate of Afghanistan in 1822 and Afghanistan in modern times. This history is largely shared with that of Central Asia, Middle East, and northern parts of the Indian subcontinent.

Human habitation in Afghanistan dates back to the early Middle Paleolithic era, and the country's strategic location along the historic Silk Road has led it to being described, picturesquely, as the ‘roundabout of the ancient world’. The land has historically been home to various different peoples and has witnessed numerous military campaigns, including those by the Persians, Alexander the Great, the Maurya Empire, Arab Muslims, the Mongols, The Mughal Empire, the British, the Soviet Union, and most recently by a US-led coalition. The various conquests and periods in the Iranian cultural spheres made the area a center for Zoroastrianism and Buddhism, and a small community of Hinduism, and later Islam throughout history.

Shortly after the September 11 attacks in 2001, the United States declared the war on terror and subsequently led a multinational military operation against Taliban-ruled Afghanistan. The stated goal was to dismantle al-Qaeda, which had executed the attacks under the leadership of Osama bin Laden, and to deny Islamist militants a safe base of operations in Afghanistan by toppling the ruling Taliban government. The United Kingdom was a key ally of the United States, offering support for military action from the start of the invasion preparations. The American military presence in Afghanistan greatly bolstered the Northern Alliance, which had been locked in a losing fight with the Taliban during the Afghan Civil War. Prior to the beginning of the United States' war effort, the Taliban had seized around 85% of Afghanistan's territory as well as the capital city of Kabul, effectively confining the Northern Alliance to Badakhshan Province and smaller surrounding areas. The American-led invasion on 7 October 2001, marked the first phase of what would become the 20-year-long War in Afghanistan.

After the September 11 attacks, American president George W. Bush demanded that the Taliban government extradite Osama bin Laden to the United States and also expel al-Qaeda militants from Afghanistan; bin Laden had been active in Afghanistan since the Soviet–Afghan War and was already wanted by the Federal Bureau of Investigation for his role in the 1998 United States embassy bombings. The Taliban declined to extradite bin Laden and further ignored demands to shut down terrorist bases or extradite other suspected terrorists. In response, the United States launched Operation Enduring Freedom on 7 October 2001, alongside the United Kingdom. The two countries were later joined by a large multinational force, including Afghanistan's local Northern Alliance. The invasion effort made rapid progress for the next two months as the coalition captured Kabul on 13 November and toppled the Taliban by 17 December, after which international military bases were set up near major cities across the country. However, most members of al-Qaeda and the Taliban were not captured: during the Battle of Tora Bora, several fighters including bin Laden, the founder of al-Qaeda escaped into neighboring Pakistan or otherwise retreated to remote regions deep within the Hindu Kush.

Operation Enduring Freedom (OEF) was the official name used by the U.S. government for both the first stage (2001–2014) of the war in Afghanistan (2001–2021) and related military operations during broader-scale global war on terrorism. On 7 October 2001, in response to the September 11 attacks, President George W. Bush announced that airstrikes against al-Qaeda and the Taliban had begun in Afghanistan. Beyond the military actions in Afghanistan, U.S military command structures operating under the Operation Enduring Freedom banner were also affiliated with several counterterrorism missions in other countries, such as OEF-Philippines and OEF-Trans Sahara.

After 13 years, on 28 December 2014, President Barack Obama announced the end of Operation Enduring Freedom in Afghanistan. Subsequent operations in Afghanistan by the United States' military forces, both non-combat and combat, occurred under the name Operation Freedom's Sentinel.

The Islamic Republic of Afghanistan was a presidential republic in Afghanistan from 2004 to 2021. The state was established to replace the Afghan interim (2001–2002) and transitional (2002–2004) administrations, which were formed after the 2001 United States invasion of Afghanistan that had toppled the partially recognized Taliban-ruled Islamic Emirate of Afghanistan. However, on 15 August 2021, the country was recaptured by the Taliban, which marked the end of the 2001–2021 war, the longest war in US history. This led to the overthrow of the Islamic Republic, led by President Ashraf Ghani, and the reinstatement of the Islamic Emirate under the control of the Taliban, today the ruling government of Afghanistan. While the United Nations still recognizes the Islamic Republic as the legitimate government of Afghanistan, this toppled government controls no portion of the country. The US–Taliban deal, signed on 29 February 2020 in Qatar, was one of the critical events that caused the collapse of the Afghan National Security Forces (ANSF). Following the deal, the US dramatically reduced the number of air attacks and deprived the ANSF of a critical edge in fighting the Taliban insurgency, leading to the Taliban takeover of Kabul.

Following the September 11 attacks, the United States and several allies invaded Afghanistan, overthrowing the Taliban's first government (which had limited recognition) in support of the opposition Northern Alliance. Afterwards, a transitional government was formed under the leadership of Hamid Karzai. After the 2003 loya jirga, a unitary presidential Islamic republic was proclaimed under a new constitution, and Karzai was elected for a full term as president. Meanwhile, the US-led international coalition helped maintain internal security, gradually transferring the burden of defense to the Afghan Armed Forces after 2013–14.

The Taliban insurgency began after the group's fall from power during the 2001 war in Afghanistan. The Taliban forces fought against the Afghan government, led by President Hamid Karzai, and later by President Ashraf Ghani, and against a United States-led coalition of forces that has included all members of NATO; the 2021 Taliban offensive resulted in the collapse of the government of Ashraf Ghani. The private sector in Pakistan extends financial aid to the Taliban, contributing to their financial sustenance.

The insurgency had spread to some degree over the border to neighboring Pakistan, in particular Khyber Pakhtunkhwa. The Taliban conducted warfare against Afghan National Security Forces and their NATO allies, as well as against civilian targets. Regional countries, particularly Pakistan, Iran, China and Russia, were often accused of funding and supporting the insurgent groups.

The 2021 Taliban offensive was a military offensive by the Taliban insurgent group and allied militants 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.