Afghanistan,[c] officially the Islamic Emirate of Afghanistan,[d] is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia,[24] it is bordered by Pakistan to the east and south,[e] 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. As of 2021, its population is 40.2 million,[7] composed mostly of ethnic Pashtuns, Tajiks, Hazaras, and Uzbeks. Kabul is the country's largest city and serves as its capital. Human habitation in Afghanistan dates back to the 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’.[25] Popularly referred to as the graveyard of empires,[26] the land has historically been home to various peoples and 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 most recently by an American-led coalition. Afghanistan also served as the source from which the Greco-Bactrians and the Mughals, among others, rose to form major empires.[27] The various conquests and periods in both the Iranian and Indian cultural spheres[28][29] made the area a center for Zoroastrianism, Buddhism, Hinduism, and later Islam throughout history.[30] The modern state of Afghanistan began with the Durrani dynasty in the 18th century, with the Durrani Afghan Empire being formed by Ahmad Shah Durrani. The Durrani Empire led conquests in which, at its peak, encompassed land that spanned from eastern Iran to northern India.[31][32] Following its decline and the death of Ahmad Shah Durrani, and Timur Shah, it was divided into multiple smaller independent kingdoms, including but not limited to: Herat, Kandahar and Kabul. Afghanistan would be reunited in the 19th century after wars of unification led by Dost Mohammad Khan, where he conquered the independent principalities in Afghanistan. Dost Mohammad died in 1863, weeks after his last campaign to unite Afghanistan, and as a result, threw Afghanistan back into civil war with his successors. During this time, Afghanistan became a buffer state in the Great Game between the British Empire (in British-ruled India) and the Russian Empire. From India, the British attempted to subjugate Afghanistan but were repelled in the First Anglo-Afghan War. However, the Second Anglo-Afghan War saw a British victory and the successful establishment of British political influence over Afghanistan. Following the Third Anglo-Afghan War in 1919, Afghanistan became free of foreign dominance, and eventually emerged as the independent Kingdom of Afghanistan in June 1926 under Amanullah Khan. This monarchy lasted almost 50 years, until Zahir Shah was overthrown in 1973, following which the Republic of Afghanistan was established. Since the late 1970s, Afghanistan's history has been dominated by extensive warfare, including coups, revolutions, invasions, insurgencies, and civil wars. Due to the effects of war, the country has dealt with high levels of terrorism, poverty, and child malnutrition. Afghanistan's economy is the world's 96th-largest, with a gross domestic product (GDP) of $72.9 billion by purchasing power parity; the country fares much worse in terms of per-capita GDP (PPP), ranking 169th out of 186 countries as of 2018. In 2021, Afghanistan was captured by the Taliban, which marked the end of the 2001–2021 war, the longest war in US history.[33] This led to the overthrowing of the Islamic Republic of Afghanistan under President Ashraf Ghani and reinstating the Islamic Emirate of Afghanistan under the control of the Taliban. 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).[34] 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.[35] Soon after, former first vice president Amrullah Saleh declared himself the caretaker president of Afghanistan and announced the resistance against the Taliban.[36][37] Afghanistan is prominently rich in natural resources. Those resources include lithium, iron, zinc, and copper, amongst many others. It is also the largest producer of opium.[38] The country is a founding member of the Organisation of Islamic Cooperation.