In 2009, President Obama announced an increase in U.S. troop levels that would happen through the end of 2009 and into 2010. See how the levels have increased even as U.S. troop levels in Iraq fall.
Almost nine years since the war in Afghanistan began, take a look at some of each year's key events.
Macedonian-born Alexander the Great led his armies through Persia and Afghanistan around 330 B.C. While Greek rule continued for the next two centuries, civil unrest and revolts were common. And in 1273, explorer Marco Polo crossed northern Afghanistan on his voyage from Italy to China. Soon, the nation became a critical, if dangerous, stop on the "Silk Route," an ancient trade route that linked Rome and China.
As more U.S. troops enter Afghanistan, take a look at some of the struggles in the history of this ancient land, where war and economic upheaval are nothing new.
Forty-seven countries have troops in Afghanistan, according to NATO's International Security Assistance Force, and the total is approximately 120,000 as of August 2010. See how many are from each nation, above. The United States, not shown, has approximately 95,000 troops there now.