US Department of Defense to continue development of nuclear B61-13 gravity bomb variant.

On October 27, the U.S. Department of Defense (DoD) announced that the United States will pursue a modern variant of the B61 nuclear gravity bomb, designated the B61-13, pending Congressional authorization and appropriation. The fielding of the B61-13 is not in response to any specific current event; it reflects an ongoing assessment of a changing security environment.
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An F-35A Lightning II drops an inert B61-12 nuclear bomb during a trial. The B-61-13 will be an enhanced variant of the B-61-12, able to penetrate deeper through reinforced concrete fortifications before exploding (Picture source : U.S. Air Force)

The Department of Energy's National Nuclear Security Administration (NNSA) would produce the B61-13. The decision to pursue this capability, which was undertaken in close collaboration with the NNSA, responds to the demands of a rapidly evolving security environment as described in the 2022 Nuclear Posture Review: "Today's announcement is reflective of a changing security environment and growing threats from potential adversaries," said Assistant Secretary of Defense for Space Policy John Plumb. "The United States has a responsibility to continue to assess and field the capabilities we need to credibly deter and, if necessary, respond to strategic attacks, and assure our allies."

The B61-13 would be deliverable by modern aircraft, strengthening deterrence of adversaries and assurance of allies and partners by providing the President with additional options against certain harder and large-area military targets. It would replace some of the B61-7s in the current nuclear stockpile and have a yield similar to the B61-7, which is higher than that of the B61-12.

"The B61-13 represents a reasonable step to manage the challenges of a highly dynamic security environment," said Plumb. "While it provides us with additional flexibility, production of the B61-13 will not increase the overall number of weapons in our nuclear stockpile."

The B61-13 would take advantage of the current, established production capabilities supporting the B61-12, and would include the modern safety, security, and accuracy features of the B61-12.
This initiative follows several months of review and consideration.

This new variant is intended to penetrate deeper through reinforced underground fortifications before exploding, creating much more sismic havoc in enemy tunnels, for instance.

Defense News October 2023