The Democratic Party's progressive presidential candidates want to end the "forever war" — America's two-decade struggle against jihadi extremism. The trouble is that they don't know how.

It is easy enough for the progressives to argue that the United States should pull back from the greater Middle East and demilitarize its counterterrorism strategy. Unfortunately, they have less to say about how the U.S. can do so responsibly.

The idea that the forever war must end has become a consensus position on the progressive left. Last November, Sen. Elizabeth Warren kicked off the 2020 foreign policy sweepstakes with a speech that condemned the war on terrorism as costly, counterproductive and morally debasing. She called for the U.S. to conclude a peace deal with the Taliban so that American forces can withdraw from Afghanistan. Likewise, Rep. Tulsi Gabbard (a combat veteran whose views blend progressivism with an array of other influences) has consistently criticized America's policies in the Middle East and advocated greater restraint.