Afghanistan is strategically placed between the Middle East, central Asia and the Indian subcontinent.
For centuries, foreign armies have fought over it and tried to conquer it.
Many have been defeated by the rugged terrain - mountains cover four-fifths of the land - and fierce resistance from the different tribal groups.
Ethnic, religious and regional rivalries and the terrain have also made it hard for the authorities in the capital, Kabul, to rule the country.
The overthrow of Afghanistan's King Zahir Shah in 1973 sparked a chain of events that led to decades of unrest.
Reforms imposed by a Moscow-backed regime sparked rebellions and, in 1979, Soviet troops invaded Afghanistan.
US-backed Islamic fighters known as mujahideen - among them Osama Bin Laden - fought the Soviets and the country became a Cold War battleground.
In 1989, the USSR withdrew in defeat, leaving behind a devastated country and hundreds of thousands of Afghans dead.
After the Soviet forces left, a number of Afghan factions continued to fight for control of the country.
In 1994, the hard-line Islamic Taleban emerged. By the late 1990s, they controlled most of Afghanistan with their strict version of Sharia law.
The Taleban angered the international community by letting Osama Bin Laden, and other al-Qaeda members, live there.
In 2001, after the 9/11 attacks on the US, the Taleban refused to hand him over, paving the way for a new war.
In October 2001, the US and its allies launched a bombing campaign against the Taleban marking the beginning of America's "war on terror".
Within weeks, US-led troops and local fighters forced the Taleban from Kabul and drove them from power.
But Taleban leader Mullah Omar and Osama Bin Laden evaded capture and are thought to have survived the offensive.
Several thousand US troops remain in Afghanistan hunting Taleban supporters who have regrouped since 2003.
Years of fighting have left Afghanistan in ruins - it is one of the poorest countries in the world.
International donors have pledged more than $10bn, but the government says it needs more.
In 2004 a constitution was signed and Hamid Karzai won the country's first direct presidential elections.
In 2005 national assembly elections were held.
Islamic militants, warlords and the booming drugs trade are among the greatest threats to stability.
The authorities have limited power outside Kabul, and huge swathes of the country are controlled by warlords once funded by the US to fight the Taleban.
Many of these powerful regional militia chiefs have a history of drug trafficking and human rights abuses.
The state of lawlessness is fuelled by the opium trade which despite a ban on poppy crops generated $2.3bn in 2003.