In an excellent article published recently, Andrew Latham makes a strong case for increasing the Air Force's buy of B-21 bombers from the current plan of 100 to a much larger number. "The 300 to 400 range? That starts to become a full-spectrum strategic force that’s credible, resilient, and able to absorb the inevitable shocks associated with warfighting."

Unfortunately, without canceling the planned retirement of B-2 bombers, which recently were key to the destruction of Iran's nuclear facilities, B-21s alone could be severely challenged to destroy future deeply buried and fortified targets.

Loss of the B-2s may eliminate the U.S. ability to deliver the Massive Ordnance Penetrator (GBU-57/B or MOP) which is by far the most effective U.S. conventional weapon against hard and very deeply buried targets. The B-2 bomber is the only U.S. bomber cleared to deliver the MOP. The smaller B-21 bomb-carrying capacity means it clearly cannot carry two MOPs. A new and lighter Next Generation Penetrator is under development and should be designed to be carried by the B-21, but its destructive capability is uncertain. Thus, without the B-2s, considerably more than 400 B-21s could be required to have a viable very-hard-and -deep-target kill capability, or the U.S. might lose that capability.

The only other options would be using B-21s to drop or launch specialized nuclear weapons against these kinds of targets or using submarine-launched or land-based missiles armed with such warheads. It is unconscionable to have only these options for future national leaders.

An alternative 500-bomber force, consisting of 360 B-21s and no B-2, B-1, or B-52 retirements has been proposed by General Mike Loh, former commander of the Air Combat Command. That option would retain today's very-hard-target kill capability by the B-2s as well as the full range of deterrence capabilities offered by the remaining B-1s and dozens of upgraded B-52s.

Yes, America needs many more bombers, mostly B-21s, but wait on retiring B-2s, B-1s, B-52s