The video of the ambush is brief and sickening. Two young National Guard soldiers, barely into adulthood, walk their post near the White House. An Islamic terrorist rounds the corner, raises a revolver, and opens fire. By the time other guardsmen tackle him, Specialist Sarah Beckstrom is fatally wounded and Staff Sgt. Andrew Wolfe is fighting for his life. The suspect, Rahmanullah Lakanwal, is not some random drifter. He is a former member of the CIA’s elite Afghan “Zero Units,” a paramilitary strike force trained for kill capture missions in the Taliban heartland. He came here through President Biden’s Operation...