GRAY AMAZONS

The U.S. Air Force has three options for deploying nuclear weapons against an enemy: intercontinental ballistic missiles launched from an underground silo, missiles fired from a submarine, and weapons carried by a bomber. With the B-21 scheduled to enter service in 2025, the Air Force has announced its intention to retire the B-1B and B-2 and sustain a fleet of 100 B-21s and 76 B-52s. The old bombers are still useful as a threatening gesture: In the event of tension with world powers such as China or Russia they would fly close to enemy airspace, where they’d be both visible and unpredictable. As General David Petraeus once wrote: “Bombers can be called back after launching or retargeted in flight in a way that missiles cannot.” Because once a nuclear missile has been launched, widespread destruction is assured within 30 minutes.