Sentinel ICBM

The LGM-35A Sentinel is the U.S. Air Force's next-generation intercontinental ballistic missile (ICBM), developed by Northrop Grumman to replace the LGM-30G Minuteman III, which has been in service since 1970. Sentinel is the ground-based leg of the U.S. nuclear triad, alongside Ohio-class submarines (and their Columbia-class successors) and strategic bombers such as the B-2 and forthcoming B-21 Raider.

Originally known as the Ground Based Strategic Deterrent (GBSD) program, the missile was redesignated "Sentinel" in April 2022. Northrop Grumman won the engineering and manufacturing development contract in September 2020 after Boeing declined to bid, citing concerns about competing against a vertically integrated rival following Northrop's acquisition of solid-rocket-motor maker Orbital ATK.

The program covers not only the missiles themselves but also the modernization of launch facilities, missile alert centers, and command-and-control infrastructure across F.E. Warren AFB (Wyoming), Malmstrom AFB (Montana), and Minot AFB (North Dakota). Sentinel is intended to maintain a force of roughly 400 deployed ICBMs, consistent with U.S. obligations under the New START Treaty framework.

The program has faced significant scrutiny. In January 2024, the Air Force notified Congress of a Nunn-McCurdy breach, with projected costs rising by more than 37 percent above baseline estimates. In July 2024, the Department of Defense certified the program to continue but ordered a restructuring, with the silo and infrastructure overhaul identified as the principal cost driver. Initial operational capability has slipped from the late 2020s to the early 2030s.

Critics, including some arms-control analysts and members of Congress, have questioned whether a new land-based ICBM is necessary or whether the Minuteman III could be life-extended further. Proponents argue Sentinel is essential to deterrence credibility amid Russian and Chinese nuclear modernization.