According to the US Department of Defense, the total military expenditure in Afghanistan (from October 2001 until March 2019) was $760bn.
But an independent study carried out by Brown University's Cost of War Project argues that the official US figures for Afghanistan are a substantial underestimate. It says they do not include spending on war veterans' care, money spent on other government departments for war-related activities and the cost of interest on debt incurred to pay for the war. It estimates the total cost, factoring in these additional elements, is closer to $1 trillion.
The bulk of the money has been spent on counter-insurgency operations, and on the needs of US troops, such as food, clothing, medical care, special pay and benefits. Official data shows the US has also contributed approximately $133bn -16% of all money spent in the last 17 years - to reconstruction efforts in Afghanistan. And more than half of that ($83bn) has gone on building up Afghan security forces, including the Afghan National Army and police force.
The US has spent on average $1.5m day - or nearly $9bn since 2002 until June this year - on anti-narcotics efforts, yet the area devoted to growing opium poppy has actually increased, according to UN figures.
In 2017, the US watchdog responsible for the oversight of reconstruction efforts said that as much as $15.5bn had been lost on "waste, fraud and abuse" over the past 11 years. That figure is probably "only a portion" of the total waste, according to the watchdog, which added that US money "often exacerbated conflicts, enabled corruption, and bolstered support for insurgents".