Crumbling missile silos are forcing a multibillion-dollar rethink of how, where and whether to base the next generation of US nuclear weapons.
This month, multiple media outlets reported that the US Air Force now expects to construct predominantly new silos for the LGM-35A Sentinel intercontinental ballistic missile (ICBM) system, abandoning plans to reuse 55-year-old Minuteman III silos after concluding that doing so poses unacceptable cost, schedule and performance risks.
Initially seen as cost-effective when Sentinel launched a decade ago, silo reuse has proven unfeasible following a failed test conversion at Vandenberg Space Force Base and subsequent analyses under the Nunn-McCurdy Act cost breach review.
In April, General Thomas Bussiere, commander of the US Air Force Global Strike Command, confirmed that reusing old silos would jeopardize affordability, timelines and technical feasibility.
As a result, the Air Force will build new silos primarily on federally owned land within existing missile fields across the states of Colorado, Montana, Nebraska, North Dakota and Wyoming.
Developed by Northrop Grumman, Sentinel aims to replace 400 aging Minuteman III missiles, but its US$141 billion price tag—driven mainly by launch infrastructure—has delayed its debut beyond 2029.
Critics, including the Federation of American Scientists (FAS), accuse the US Department of Defense (DOD) and its contractor of mismanagement and underestimating the program’s complexity. Still, officials insist Sentinel is essential to preserving the nuclear triad and must proceed despite soaring costs and logistical obstacles.
Time and Wall Street Journal (WSJ) reports describe near-daily breakdowns, water intrusion, misaligned doors, collapsed conduits and obsolete parts, some reportedly sourced from museums. Silo modernization now requires full reconstruction of command centers and thousands of kilometers of new fiber optics, those reports said.
But infrastructure woes aren’t the only factor driving debate—there’s also disagreement over whether fixed ICBMs still belong in the triad.
Steve Fetter and Kingston Reif argued in an October 2019 War on the Rocks piece that silo-based ICBMs act as a “sponge” deterrent: with 450 silos spread across vast territory, an adversary would need to expend hundreds of warheads to disable them in a first strike.
They also serve as a tripwire, guaranteeing retaliation if the US homeland is attacked, and provide a hedge against possible vulnerabilities in nuclear ballistic missile submarines (SSBN) and strategic bombers.
However, they warned that fixed ICBMs must be launched within 30 minutes of an incoming strike, giving the president less than 10 minutes to decide, raising the risk of mistaken retaliation based on incomplete data.
If submarines and bombers are already on alert and dispersed, they argued, they offer more than enough retaliatory capability, making silo-based missiles redundant in both survivability and flexibility.
However, if an SSBN is destroyed, unable to launch or loses contact with command, its entire missile load is lost. Thomas Mahnken and Bryan Clark noted in a June 2020 The Strategist piece that with as few as one SSBN on patrol at a time, a single loss could cripple a third of the triad.
Emerging sensor technologies could soon render oceans transparent, challenging the future viability of sea-based deterrents.
Likewise with strategic bombers, Sidney Dean pointed out in a December 2022 article for European Security and Defense (ESD) that they rely on forward bases with fixed locations, making them and their infrastructure susceptible to preemptive attack.
Dean noted that ICBMs can reach targets in under 30 minutes, while bombers may take hours to reach their weapon deployment zones, giving adversaries ample time to track, intercept or mount defenses. He added that bombers are vulnerable to enemy air defenses, interceptors and electromagnetic pulse (EMP) attacks.
Given the mounting vulnerabilities of all triad legs—fixed, sea and air—combined with rising costs, the 2023 US Strategic Posture Report recommended that some ICBMs be deployed in a road-mobile configuration to mitigate silo limitations.
In a January 2024 Heritage Foundation article, Robert Peters endorsed this approach, suggesting that road-mobile Sentinels on transporter erector launchers (TELs) would be difficult for adversaries to target.
Peters suggested that in a crisis or for signaling, mobile ICBMs could operate on randomized, pre-approved routes, moving hundreds of kilometers daily, making them nearly impossible to target.
He added that mobile ICBMs could head to launch sites to await further orders if an attack were detected, significantly enhancing survivability.
Yet the mobile option introduces its risks. Brian Wish, writing in a Real Clear Defense article, warned that mobile ICBMs are more vulnerable to terrorist attacks, politically controversial if deployed on public roads and logistically difficult to keep on constant alert.
He argued that they should only supplement—not replace—a hardened, dispersed single-warhead silo-based arsenal, which he views as the most stable configuration for nuclear deterrence.
