January: U.S. Defense Secretary Robert Gates tells Congress that Afghanistan is the new Obama administration's "greatest test."
February: Up to 20 NATO countries pledge to increase their military and other commitments to Afghanistan after the U.S. announces the dispatch of 17,000 extra troops to the country.
March: President Barack Obama unveils a new strategy for Afghanistan and Pakistan to combat what he calls an increasingly perilous situation. He says an extra 4,000 U.S. personnel will train and bolster Afghan soldiers and police officers, and there will be support for civilian development.
April: Afghan President Hamid Karzai says he will seek re-election in August.
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May: Gates replaces the commander of U.S. forces in Afghanistan, Gen. David McKiernan, with Gen. Stanley McChrystal, saying the Afghan war needs "new thinking."
July: The U.S. army launches a major offensive, involving about 4,000 Marines and 650 Afghan soldiers, against the Taliban's heartland in southern Helmand province.
August: Elections are marred by widespread Taliban attacks, patchy turnout and claims of fraud.
September: Gen. McChrystal sends his initial assessment of Afghanistan to President Obama, asking for between 40,000 and 80,000 more U.S. troops to add to the 65,000 American soldiers already in the country.
SOURCES: BBC News and The New York Times