U.S. troops officially entered Afghanistan on Oct. 7, 2001 under Operation Enduring Freedom following the Sept. 11, 2001 terrorist attacks. The mission’s stated goal was to capture or kill al-Qaida leaders, remove the Taliban from power, and prevent terrorists from using Afghanistan as a base for launching future attacks.
Unofficially, U.S. troops had already been in Afghanistan for decades. CIA and American paramilitary forces arrived in Afghanistan prior to the Soviet Union's invasion of the country in December 1979. American military personnel helped train and arm anti-Communist forces and continued to conduct operations in Afghanistan throughout the 1980s.
Following the withdrawal of Soviet troops in 1989, American military personnel worked with local fighters to restore order and bring pro-Western leaders to power. During the years of civil war in the 1990s, American operatives worked with various factions to establish a democratic government. U.S. troops also conducted air strikes and military raids to destroy al-Qaida training camps following the 1998 bombings of American embassies in Kenya and Tanzania and the Taliban’s refusal to turn over Osama bin Laden for questioning.