(NewsNation) — The United States combat mission in Afghanistan following the 9/11 attacks ended up being America’s longest war at nearly 20 years to the day. It was also the nation’s most expensive.

The Costs of War project at Brown University reported the price tag of the war on terror stands at $2 trillion. But since the money was borrowed, when all the interest charges are tallied, the number is expected to triple by 2050 and wind up costing American taxpayers close to $6.5 trillion.

The cost of war isn’t only measured in money — a Washington Post analysis found around 800,000 soldiers served in Afghanistan in the nearly two-decade-long war, and around 2,500 never came home.

And the numbers in Afghanistan pale to those on the other front lines in Iraq, where 1.1 million soldiers served and 5,500 were killed.