In private discussions with his aides, President Trump has devised an eye-popping formula to address one of his long-standing complaints: that allies hosting U.S. forces don’t pay Washington enough money.

Under the formula, countries would pay the full cost of stationing American troops on their territory, plus 50 percent more, said U.S. and foreign officials familiar with the idea, which could have allies contributing five times what they provide.

This perspective seems backwards.

If stationing U.S. troops in, say, the Middle East prevents 9/​11’s or other terrorist attacks against the U.S., then the direct expenditures is a small price to pay.

But if U.S. troops, bases, invasions, and occupations increase resentment of the U.S. and make attacks more likely, then any reduction in expenditure that keeps our troops abroad is penny-wise but pound-foolish.

Plus, a forward-deployed military posture has other costs, as detailed by Cato’s John Glaser here.

Determining the impact of our foreign interventions on terrorism is admittedly a difficult task.

But that is the crucial question; not whether we, or they, pay for the expenditure.