The country of Afghanistan has been conquered by many foreigners beginning with Alexander the Great, but none have been able to establish control over its fiercely independent population and rugged terrain. In 1979, the Soviet Union overthrew its own puppet leader and invaded Afghanistan, only to withdraw after almost a decade of frustration, death, and expense.
During the period when local Islamic militants were fighting the Soviet troops, the United States, through the CIA primarily, furnished weapons and training. Among those fighting the Soviets was the Saudi expatriate Osama bin Laden, who established al-Qaeda and eventually staged the attacks on the World Trade Center in New York on September 11, 2001.
In retaliation for the attack, the United States first demanded that Afghanistan turn over bin Laden and when the Taliban, who were running the country at the time, refused, the United States invaded in the fall of 2001.
The Taliban were easily overthrown and plans were drawn up for democratization of Afghanistan and improvements in its economy. However, not enough resources were supplied, particularly after the invasion of Iraq to completely eradicate the Taliban resistance, which grew stronger after its initial nadir. After various attempts to win the confidence and support of the population, made difficult by its partnership with a corrupt government and a semi-hostile ally in Pakistan, the United States has begun to reduce its commitment with the intent of ending the longest war in its history.