When we consider whether to deploy U.S. military forces to war, and then keep them at war, our assessment should focus singularly on strategic need. Put simply: Where does the balance fall between protecting America’s security and interests and suffering American casualties? Financial costs should be a very distant factor in our deliberations.

I note this in light of President Trump’s decision to reduce the U.S. military force presence in Afghanistan and Iraq significantly. Force levels in Afghanistan will fall from 4,500 to 2,500 and from 3,000 to 2,500 in Iraq. These withdrawals can be justified on a simple basis: It’s what Trump promised the voters in 2016. But these withdrawals cannot be justified as a continuation of Trump’s counterterrorism strategy.