Darius I and Alexander the Great were the first to use Afghanistan as the gateway to India. Islamic conquerors arrived in the 7th century, and Genghis Khan and Tamerlane followed in the 13th and 14th centuries.

In the 19th century, Afghanistan became a battleground in the rivalry between imperial Britain and czarist Russia for control of Central Asia. Three Anglo-Afghan wars (1839–1842, 1878–1880, and 1919) ended inconclusively. In 1893 Britain established an unofficial border, the Durand Line, separating Afghanistan from British India, and London granted full independence in 1919. Emir Amanullah founded an Afghan monarchy in 1926.

During the cold war, King Mohammed Zahir Shah developed close ties with the Soviet Union, accepting extensive economic assistance from Moscow. He was deposed in 1973 by his cousin Mohammed Daoud, who proclaimed a republic. Daoud was killed in a 1978 coup, and Noor Taraki took power, setting up a Marxist regime. He, in turn, was executed in Sept. 1979, and Hafizullah Amin became president. Amin was killed in Dec. 1979, as the Soviets launched a full-scale invasion of Afghanistan and installed Babrak Karmal as president.

The Soviets, and the Soviet-backed Afghan government, were met with fierce popular resistance. Guerrilla forces, calling themselves mujahideen, pledged a jihad, or holy war, to expel the invaders. Initially armed with outdated weapons, the mujahideen became a focus of U.S. cold war strategy against the Soviet Union, and with Pakistan's help, Washington began funneling sophisticated arms to the resistance. Moscow's troops were soon bogged down in a no-win conflict with determined Afghan fighters. In 1986 Karmal resigned, and was replaced by Mohammad Najibullah. In April 1988 the USSR, U.S., Afghanistan, and Pakistan signed accords calling for an end to outside aid to the warring factions. In return, a Soviet withdrawal took place in Feb. 1989, but the pro-Soviet government of President Najibullah was left in the capital, Kabul.

By mid-April 1992 Najibullah was ousted as Islamic rebels advanced on the capital. Almost immediately, the various rebel groups began fighting one another for control. Amid the chaos of competing factions, a group calling itself the Taliban—consisting of Islamic students—seized control of Kabul in Sept. 1996. It imposed harsh fundamentalist laws, including stoning for adultery and severing hands for theft. Women were prohibited from work and school, and they were required to cover themselves from head to foot in public. By fall 1998 the Taliban controlled about 90% of the country and, with its scorched-earth tactics and human rights abuses, had turned itself into an international pariah. Only three countries—Pakistan, Saudi Arabia, and the UAR—recognized the Taliban as Afghanistan's legitimate government.

In Sept. 2001, legendary guerrilla leader Ahmed Shah Masoud was killed by suicide bombers, a seeming death knell for the anti-Taliban forces, a loosely connected group referred to as the Northern Alliance. Days later, terrorists attacked New York's World Trade Center towers and the Pentagon, and Bin Laden emerged as the primary suspect in the tragedy.

On Oct. 7, after the Taliban repeatedly and defiantly refused to turn over Bin Laden, the U.S. and its allies began daily air strikes against Afghan military installations and terrorist training camps. Five weeks later, with the help of U.S. air support, the Northern Alliance managed with breathtaking speed to take the key cities of Mazar-i-Sharif and Kabul, the capital. On Dec. 7, the Taliban regime collapsed entirely when its troops fled their last stronghold, Kandahar. However, al-Qaeda members and other mujahideen from various parts of the Islamic world who had earlier fought alongside the Taliban persisted in pockets of fierce resistance, forcing U.S. and allied troops to maintain a presence in Afghanistan. Osama bin Laden and Taliban leader Mullah Muhammad Omar remained at large.

In Dec. 2001, Hamid Karzai, a Pashtun (the dominant ethnic group in the country) and the leader of the powerful 500,000-strong Populzai clan, was named head of Afghanistan's interim government; in June 2002, he formally became president. The U.S. maintained about 12,000 troops to combat the remnants of the Taliban and al-Qaeda, and about 31 nations also contributed NATO-led peacekeeping forces. In 2003, after the United States shifted its military efforts to fighting the war in Iraq, attacks on American-led forces intensified as the Taliban and al-Qaeda began to regroup.

President Hamid Karzai's hold on power remained tenuous, as entrenched warlords continued to exert regional control. Remarkably, however, Afghanistan's first democratic presidential elections in Oct. 2004 were a success. Ten million Afghans, more than a third of the country, registered to vote, including more than 40% of eligible women. Karzai was declared the winner in November, taking 55% of the vote, and was inaugurated in December.

In May 2005, 17 people were killed during anti-American protests prompted by a report in Newsweek that American guards at the prison at Guantánamo Bay, Cuba, had desecrated the Koran. In September 2005, Afghanistan held its first democratic parliamentary elections in more than 25 years.

The Taliban continued to attack U.S. troops throughout 2005 and 2006—the latter becoming the deadliest year for U.S. troops since the war ended in 2001. In 2004 and 2005, American troop levels in Afghanistan had gradually increased to nearly 18,000 from a low of 10,000. Throughout the spring of 2006, Taliban militants—by then a force of several thousand—infiltrated southern Afghanistan, terrorizing local villagers and attacking Afghan and U.S. troops. In May and June, Operation Mount Thrust was launched, deploying more than 10,000 Afghan and coalition forces in the south. About 700 people, most of whom were Taliban, were killed. In Aug. 2006, NATO troops took over military operations in southern Afghanistan from the U.S.-led coalition. NATO's Afghanistan mission is considered the most dangerous undertaken in its 57-year history.

Attacks by the Taliban intensified and increased in late 2006 and into 2007, with militants crossing into eastern Afghanistan from Pakistan's tribal areas. The Pakistani government denied that its intelligence agency has supported the Islamic militants, despite contradictory reports from Western diplomats and the media.

Mullah Dadullah, a top Taliban operational commander who has organized assassinations and abductions, was killed in a raid in Helmand Province in May 2007 carried out by Afghan security forces, NATO troops, and American soldiers.

An August 2007 report by the United Nations found that Afghanistan's opium production doubled in two years and that the country supplies 93% of the world's heroin. Southern Afghanistan, particularly Helmand Provice, saw the largest spike, and the report said the Taliban is involved in the business.

The Taliban continued to launch attacks and gain strength throughout 2007 and into 2008. In February 2008, U.S. Secretary of State Robert Gates warned NATO members that the threat of an al-Qaeda attack on their soil is real and that they must commit more troops to stabilize Afghanistan and counter the growing power of both al-Qaeda and the Taliban.