But . . . it is flat wrong.
More comprehensive assessments, which look at direct and indirect expenditures from the wars in Iraq, Afghanistan Pakistan and Syria, estimate the cost at about $3.6 trillion from 2001 to 2016, according to a Brown University study. That figure includes costs tied to veterans' care and disability benefits, along with “war-related additions” to the Department of Homeland Security, the Pentagon and the State Department.
As our fact-checkers report, the number Trump is citing seems to come from another Brown University report, one that estimates future spending all the way out to 2050. His figure also seems to include, they write, matters such as “interest on the debt and veterans' care for the next three decades.” (A working paper from professors at Harvard Kennedy School estimated the wars in Iraq and Afghanistan would ultimately cost taxpayers $4 trillion to $6 trillion.)
Here is another thing about the president's tweet: Despite what he said on the campaign trail, Trump has expanded the war effort in Afghanistan. He approved a troop surge there, a decision that added billions to the overall cost of the war in that country. As my colleague Steven Mufson reported, Trump's “decision to send more troops will add billions of dollars a year to the already-towering war costs, which have topped $1 trillion in Afghanistan alone over the past 16 years. And the government will still be paying for war veterans' health-care costs for at least another half-century.”
Mufson wrote that U.S. spending in Afghanistan will rise to about $840.7 billion if the president's fiscal 2018 budget is approved. (That estimate comes courtesy of Anthony Cordesman, an expert at the Center for Strategic and International Studies.)