evidence: Here's what 20 years of war has done to the Afghan people. As the US withdraws its troops, we look at the latest figures on human suffering. [...] Over the 20-year war, 50 NATO and partner nations contributed forces to the missions in Afghanistan. At its peak in 2011, nearly 140,000 US and allied forces were in the country. [...] The war in Afghanistan is estimated to have cost the US $2.26 trillion to date, according to the Cost of War project. The bulk of the spending, $933bn, was allocated to the US Department of Defense war budget, later supplemented by another $443bn.