Soldiers in Afghanistan from the 3rd Infantry Division, 82nd Airborne Division and the 40th Infantry Division.

Soldiers in Afghanistan from the 3rd Infantry Division, 82nd Airborne Division and the 40th Infantry Division. U.S. Army / John Martinez

How Much Has the US Spent to Fight Terror? Here's a Guess

Are we spending too much? Too little? The picture is only growing cloudier.

Seventeen years after the fall of the twin towers and the beginning of the “Global War on Terror,” the United States still has no clear sense of what it’s spent on counterterrorism. Now, as the Pentagon begins to shift gears back to great-power competition, our inability to know what we’ve spent on CT makes it difficult to say whether we are currently spending too much or not enough. Worse, the picture is getting cloudier.

In an effort to tote up counterterrorism spending since 9/11, to examine gaps in the understanding of this spending, and to suggest ways to better account for these expenditures, the Stimson Center convened a nonpartisan study group of top experts, including two former Pentagon comptrollers. Our research suggests that the U.S. has spent $2.8 trillion on CT since 9/11, increasing counterterrorism spending’s share of total discretionary spending from less than 2 percent in 2001 to 22 percent at its peak in 2008, and just under 15 percent today.

But this data is inaccurate, because of a number of weaknesses that limit accuracy and contribute to an overall lack of transparency. These weaknesses make it difficult to evaluate whether CT spending has been effective at improving security at home and overseas.

First and foremost, inconsistent definitions across agencies lead to confusion at the highest levels. This begins at the White House’s Office of Management and the Budget, whose guidance regarding “CT spending” has shifted over time. These definitions are interpreted differently by different agencies, each of which tends to emphasize its own mission, and that leads to non-standard ways of counting “CT funding.”

Defense and State Department data is further clouded by a war-funding account that increasingly includes funds unrelated to war. At the Defense Department, nonwar spending in Overseas Contingency Operations fund grew from $10 billion in fiscal 2014 to $18 billion in fiscal 2017. And the issue likely goes much deeper. In 2016, the Pentagon acknowledged that half of its OCO fund — $30 billion — went for predictable day-to-day operations. This shift in base spending makes it more difficult to track DOD’s CT spending in the OCO budget.

Further confusion results when DoD strategists and analysts conflate the very different missions of counterinsurgency and counterterrorism.

What’s worse: The transparency of current data is eroding. This year, OMB stopped issuing an annual report that described homeland security spending in different areas of government — ending a valuable, if imperfect, resource for understanding this aspect of CT spending.

After more than a decade and a half of focus on the fight against terrorism, the Pentagon must carefully consider its next move. While spending should not be at the forefront of any strategic decision, failure to carefully consider the use of finite resources will result in missed opportunities and potentially dangerous shortcomings. In order to prepare for the future, the U.S. must, at the very least, have a clear sense of its past.