Afghanistan has been a significant U.S. foreign policy concern since 2001, when the United States, in response to the terrorist attacks of September 11, 2001, led a military campaign against Al Qaeda and the Taliban government that harboured and supported it. In the intervening 18 years, the United States has suffered approximately 2,400 military fatalities in Afghanistan, with the cost of military operations reaching nearly $750 billion. Congress has appropriated approximately $133 billion for reconstruction. In that time, an elected Afghan government has replaced the Taliban, and most measures of human development have improved, although Afghanistan's future prospects remain mixed in light of the country's ongoing violent conflict and political contention.