Peacekeeper by Fits and Starts

Feb. 26, 2019

A Peacekeeper ICBM in a modified Minuteman site at Vandenberg AFB, Calif. Development of the Peacekeeper missile began in 1972. Photo: AFA library

The Minuteman intercontinental ballistic missile—backbone of the US strategic deterrent throughout the Cold War—entered service in 1962, deployed in underground silos across the Great Plains and along the northern tier of the United States.

Even then, it was understood that silo basing was less than optimal. The original plan was that part of the Minuteman force would be mobile, with missiles moving around the countryside on railroad cars. Funding for three mobile squadrons was canceled in 1961 for reasons of cost and doubts about its necessity.

That decision took on a different cast in 1966 when the Soviet Union introduced the SS-9, a huge ICBM with extraordinary accuracy and high destructive yield. The obvious target for such a weapon was the silo-based Minuteman. By the early 1970s, the Soviets had fielded the SS-18, an improved version of the SS-9, and was testing several more new ICBMs.

The consensus of defense planners was that instead of an improved Minuteman, what was needed was a new missile, more powerful and less vulnerable. Advanced development on Missile System X—or MX, later known as Peacekeeper—began in 1972.

The driving objective of the MX/Peacekeeper program was survivability under attack, to be achieved by some combination of mobility and hardening of missile sites. Initially, the Air Force favored launching the MX by dropping it from an airplane, but that soon gave way to other concepts.

Eventually, more than 30 different basing modes were considered. They included shuttling the missiles around by road or rail, hiding them in underground tunnels, and situating the silos on the southern side of steep mountains, where they would be more difficult targets for Soviet missiles arriving from the north.

This constant jumping from one operational concept to another—often with conflicting claims about what would work and what wouldn’t—undercut credibility. MX/Peacekeeper was further bogged down by partisan opposition, which regarded any new US strategic weapons as destabilizing.

The program was repeatedly redefined and reorganized for 20 years with the result that when the Cold War ended, the operational Peacekeeper had never gotten beyond deployment in old Minuteman silos.

The quest for a mobile MX Peacekeeper was abandoned in 1991, and the missile was deactivated altogether in 2005.

The buried trench concept featured a missile on an unmanned vehicle moving back and forth along an underground trench. The option was costly, and would have had significant environmental impact. Illustration: AFA library


The SS-9, almost twice the size of Minuteman, entered flight testing in 1963.

The earliest models were not accurate enough to knock out US silos, but the launch control centers were at risk. A number of improvements reduced the immediate danger to the LCCs, but in the long term, the SS-9 was clearly a potential threat to Minuteman.

US planners had not forgotten about ICBM mobility. From 1966-1967, STRAT-X, a Pentagon study on the future of strategic weapons, reviewed ways to make missiles more survivable, including launch from airplanes and deployment on trucks moving around a winding system of roads.

In 1969, Secretary of Defense Melvin Laird declared that the SS-9 was a bid by the Soviet Union to achieve a “first strike” capability, a devastating blow to the US strategic forces. His deputy secretary, David Packard, said—disputed by arms control advocates and others—that the SS-9 had attained sufficient accuracy to destroy a Minuteman silo.

A new generation of Soviet ICBMs appeared in 1973, replacing the SS-9 with the massive SS-18 and including upgraded variants of two smaller missiles. At least one more missile was in testing, with across-the-board gains in guidance and payloads.

The Pentagon gave assurance that enough Minuteman missiles could still ride out a Soviet strike to deliver a punishing counterattack. However, future improvements in Soviet accuracy and delivery systems might chip away at that capability.

The Air Force regarded Minuteman technology as obsolete, though, and wanted the eventual replacement to have the capability for a US strike on Soviet ICBMs—not possible with the existing Minuteman.

“Air Force and Defense Department planners appear to be moving toward the conclusion that the Air Force’s next ballistic missile system should be mobile, and most likely air mobile,” Air Force Magazine reported in 1973.

In a test in October 1974, a Minuteman I missile was dropped from high over the Pacific by a C-5A transport. The missile, mounted on a carriage, was pulled out the rear door by drogue parachutes and held upright until it fell to 8,000 feet, where the engines ignited. The air launch was a complete success.

The multiple shelter concept was essentially a “shell game” in the desert. Each missile could be hidden in any one of 23 shelters. Illustration: AFA library


During the 1970s, the Air Force explored a wide range of basing options for MX, with numerous variations spun off from the principal concepts. Among the proposals actively considered were these:

Deep underground basing in hardened silos buried at depths of 1,000 to 2,000 feet.

Locating the silos on the southern side of steep mountains or mesas, creating a targeting problem for Soviet missiles fired across the polar regions to the north. As it turned out, relatively few sites could be found that were both suitable and available. Also, the Soviets might be able to shoot the tops off the mesas and bury the missile sites in radioactive rubble.

The “spoked wheel,” with a high-speed missile transporter at the hub, dashing out on warning to hardened shelters at the end of the spokes. This was somewhat akin to the Multiple Protective Shelter solution later in effect from 1979 to 1981.

The “buried trench,” with the missile on an unmanned vehicle moving back and forth along an underground trench, five feet below the surface and 20 miles long. This option was costly, and had significant environmental impact.

In 1976, Secretary of Defense James R. Schlesinger proposed deploying MX in existing Minuteman silos as a temporary expedient, but Congress would not fund it, directing validation of either a buried trench or shelter basing plan. Congress also turned down air-mobile basing.

Meanwhile, both Minuteman (in 1970) and the SS-18 (in 1975) had gained multiple independently targetable re-entry vehicles or MIRVs and could deliver between three and 10 warheads per missile.

Drew Middleton of The New York Times was among those pointing out that the US Air Force was still “talking in conceptual terms about the MX,” whereas “the Russians have developed and produced four new ICBMs,” referring to the SS-17, SS-18, SS-19, and the SSX-16-X, then under development.

The rail garrison concept consisted of 25 missile trains, each carrying two Peacekeepers. Specially designed rail cars would transport the missiles and serve as launchers. Illustration: Convair/General Dynamics


Ironically, it fell to President Jimmy Carter—who wanted passionately to cut the defense budget and reach a SALT II arms control agreement with the Russians—to revive the lagging MX program. In the opinion of The New York Times, “Approval of the MX was the price President Carter thought he had to pay for Air Force support of the SALT II treaty, and he paid it.”

In 1979, Carter acknowledged that fixed-based missiles were “becoming vulnerable to attack” and authorized full-scale development of MX to be deployed in Multiple Protective Shelters, a “shell-game” arrangement in the deserts of Nevada and Utah.

It provided for 200 “racetracks” or long oval roadways. Each of them was a 15-mile closed loop with 23 spur roads leading off of it to concrete and steel shelters. One MX would be assigned to each racetrack, able to take cover in any of the 23 shelters. For arms control verification, the shelters would have a removable “plug” in the roof, to be opened at specific intervals to allow the Soviets to see that there was only one MX per racetrack.

“The system consists of a missile, a transporter or fancy truck, a shelter or concrete bunker, a launcher decoy, and some cheap roads,” said Deputy Undersecretary of Defense Seymour Zeiberg. “For security reasons, a two-and-one-half-acre plot around the shelters will be fenced off. … The fenced area is the same as we use in the Minuteman bases. We expect that farming and grazing can be right up to the fence. … The roads connecting the shelters will be as simple as we can get away with.”

The footprint of the project was significantly greater than that, said local ranchers and farmers who were opposed to it. True, the total “public exclusion zone” was 33 square miles, but the clusters were not bunched together into a single space. The total deployment area took in about 15,000 square miles, some of which might be closed off in times of increased security.

That, along with more than 10,000 miles of connecting and service roads, would change the character of the desert region. Furthermore, the project would use large amounts of water, especially during construction, and deplete scarce ground water reserves. The governors of Nevada and Utah did not want the missiles in their states.

Speaking for those with more fundamental objections, The New York Times declared that, “The MX would threaten Soviet missiles in underground silos and thus provide Soviet generals with a compelling argument for shooting first in a crisis.”

During the 1980 election campaign, Republican Ronald Reagan was critical of Carter’s Multiple Protective Shelters plan and canceled it when he became president, even though he was convinced of the need for the missile. That left him in search of an alternative basing option.

Soviet Military Power, a major report from the Pentagon published in October 1981, said that upgrades to the SS-18 had reached the point where each of its 10 warheads “has a better than 50 percent chance of destroying a Minuteman silo.”

The Boeing version (r) and the Martin Marietta version of the small ICBM hard mobile launcher during mobility testing at the Yuma Proving Ground in Arizona in 1986. Photo: Garfield Jones/DOD via National Archives


In November 1982, Reagan gave the MX a name—Peacekeeper—and proposed a deployment mode called Closely Spaced Basing, or “Dense Pack.” The array would have 100 Peacekeeper silos, spaced about 2,000 feet apart and all grouped onto a single site no larger than 15 square miles.

The first incoming Russian missiles would detonate and wipe out some of the Peacekeepers. However, the attack would also leave behind lingering heat and radiation, setting up “fratricide” that would disable or destroy the following waves of Soviet missiles as they arrived.

Carter said that Dense Pack sounded “ridiculous.” Critics ridiculed it as “Dunce Pack,” but Pentagon officials said it would work, and that about half of the Peacekeepers would survive a Soviet strike. The nuclear effects would persist long enough for the remaining Peacekeepers, carrying 250 to 500 warheads, to launch a retaliatory counterattack.

Rep. Barney Frank (D-Mass.) said the string of odd-sounding proposals for MX were “like critics of the Three Stooges debating the right way to squirt seltzer up your nose.”

Congress would not buy the Dense Pack idea and refused to fund it. Reagan then fell back on a commission on strategic forces, headed by Brent Scowcroft, to suggest the next steps. Scowcroft, reporting in April 1983, proposed a two-part program, to which Reagan agreed.

To fill the hard-target capability gap, 100 Peacekeeper missiles would be deployed in existing Minuteman silos. Concurrently, a small single-warhead ICBM would be developed for deployment in a mobile mode for survivability.

The small missile was promptly dubbed “Midgetman.” To some extent, the particular capabilities of each missile system would offset the shortcomings of the other.

The plan represented a political compromise, sufficient to keep the program going, although it suffered somewhat in credibility. After years of hearing about the vulnerability of Minuteman in silos, the public did not understand why, all at once, Peacekeeper in those same silos was acceptable.

The first flight test of Peacekeeper took place in June 1983. Production began in February 1984. The first 10 Peacekeepers went on alert in modified Minuteman silos at Francis E. Warren Air Force Base near Cheyenne, Wyo., in December 1986.

Midgetman, projected to be operational in 1992, would be stationed at Air Force installations from which it could fan out on 15 minutes warning to roadways in hardened mobile launch vehicles. It would have the capability to retarget quickly and launch from a dispersed location.


There would be one last shot at a mobile Peacekeeper. In 1985, Congress set a ceiling of 50 missiles on the program until the administration came up with a more survivable basing plan. In December 1986, Reagan proposed Peacekeeper Rail Garrison. It was a variation on an approach the Air Force had worked up for the early Minuteman two decades before.

The rail garrison system consisted of 25 missile trains, each of them carrying two Peacekeepers. Specially designed rail cars would transport the missiles and serve as launchers. Day to day, the trains would be parked in special “igloos” on military bases. Each “garrison” would consist of about 50 acres of land and use several igloos to house the trains. In time of crisis, the trains would move out onto the 200,000 miles of commercial rail track.

Gen. Larry D. Welch, Air Force Chief of Staff, said in 1987 that “survivability has been overplayed. The real issue is capability.” ICBMs, he said, “are at present our only prompt hard-target capability for the foreseeable future.”

Welch pointed out that of all the preparatory steps possible in response to crisis, “the least provocative is putting Peacekeeper on the rails.” This could be done on the softest of warning indications.

Opponents disagreed. Sen. Albert D. Gore Jr. (D-Tenn.) said that rolling out Peacekeeper would change the equation of power and confront the Soviet Union with a limited window of time to strike without losing advantage.

Midgetman, he said, could be ready with less warning and without the risk of destabilizing the crisis.

Rail garrison edged forward slowly, and a prototype rail garrison car was delivered in October 1990. Design work continued on Midgetman.


Neither program had reached completion when the Cold War ended.

Development of the Peacekeeper rail garrison system was terminated in 1991.

The prototype rail garrison car was sent to the US Air Force museum in 1994.

Midgetman was never built, and the program was canceled in 1992.

The Peacekeeper missiles intended for rail garrison deployment were installed instead in Minuteman silos. Then in 2005, Peacekeeper was deactivated, replaced in the silos by Minuteman III missiles refitted with the newer and more powerful warheads from the now-retired MX Peacekeepers. In accordance with arms control agreements, all of the Minuteman IIIs were downgraded to single-warhead status in 2014.

The search for deployment options had come full circle. The technology had improved, of course, but the configuration and the basing mode for the ICBM force today—single-warhead Minuteman missiles in hardened silos—are the same as they were in the beginning, 60 years ago.

At long last, Minuteman today is approaching the end of its run. In 2017, the Air Force awarded contacts to explore the next generation of ICBMs, called the Ground-Based Strategic Deterrent. Specific proposals for building the system are expected in 2020.

John T. Correll was editor-in-chief of Air Force Magazine for 18 years and is a frequent contributor. His most recent article, “U-2 Down,” appeared in the January/February issue.