Foreign Relations of the United States, 1977–1980, Volume IV, National Security Policy

137. Memorandum From Denis Clift, John Matheny, and Ralph Crosby of the Vice President’s Staff to Vice President Mondale¹

Washington, May 24, 1979

SUBJECT

• PRC on MX Basing, Friday, May 25, 1979, 2:00 p.m., Situation Room

The third PRC (principals only) on MX Basing will be held on May 25. We recommend that you attend. The candidates for MX basing have now been narrowed to three from the original list of five:

— ICBMS in Trenches. This concept was first introduced at the last PRC and consists of a series of 25-mile long trenches with several rail cars carrying missiles running back and forth within each trench. The trenches are covered with removable concrete slabs. This option would run anywhere from $6 to $10 billion more than MPS and appears to have no advantages (if MPS uses horizontal shelters) other than being able to shift missiles more quickly during crisis buildup to enhance security. OSD currently favors this option because they believe it has a better chance of Presidential approval than MPS.

— MPS: The Multiple Protective Structure (MPS) System (the preferred option, in fact, of OSD and JCS)—this time with an added feature of horizontal vice vertical shelters to ease verification concerns (this is the only one of the original options which has basically remained intact).

— Common M–X/Trident II in SILOs, at Sea and Aboard Aircraft—a partly common missile for use in Trident submarines (more capable missile, therefore less submarines), in STOL aircraft and in fixed SILOs. This option also accelerates the cruise missile carrier program. This is a hybrid (costing more than the other two options) which features the largest increase in warheads per dollars spent (an analyst’s dream), but which also dodges the question of a new large ICBM (“partly common” is smaller than the original M-X) and abandons our land based missiles to their present highly vulnerable deployment mode. (As noted in the NSC memorandum, this is really not a politically feasible option—it does not restore survivability of the ICBM.)

What is not explicit in the PRC preparatory material is that the President has made it clear on a number of occasions that he has a great problem with MPS, although the Defense community (together with OMB and the NSC) are almost universally for it.

The President is concerned over what he perceives to be more difficult verification problems than are thought to be the case by his advisors; he believes that the Soviet response might be to produce more reentry vehicles to defeat MPS or even try to “breakout” by duplicating MPS in an unverifiable manner, thus escalating the arms “race.”

Ironically, the MPS system, if deployed, may have precisely the opposite effect. By decoupling the force size from survivability, we are forcing the Soviets to “come clean” as to their intentions. By the end of the current SALT treaty, they will have matched us in total number of reentry vehicles—this can be done within SALT constraints if they MIRV their SLBMs with smaller RVs—the final political plateau to perceived Soviet equality. Should the Soviets seek to further fractionate their ICBM RVs to try to defeat MPS (a violation of SALT II), they are clearly moving in a counterforce direction and there can be no argument as to their intent. Even if this were the case, however, we can build holes in the ground as fast and as cheaply as they can build new RVs, and the absurdity of that exercise may drive both sides to finally reduce forces.

This third PRC is preparatory to an NSC meeting on June 6² at which time the President is expected to reach a decision. Your entrance at this point in time into the deliberation process would serve to make you fully aware of the pros and cons for each MX basing option. We recommend that you attend.

As you know, while no one in authority is saying so publicly, a positive decision by the President on MX is seen as vital by the Joint Chiefs. This decision, in turn, cannot help but influence the final position of the Chiefs on SALT II.

1. Source: Carter Library, Donated Material, Papers of Walter F. Mondale, National Security Council Meetings, 1977–1980, Box 100, NSC Meetings, [6–12/1979]. Secret.
2. The NSC meeting was held on June 4. See Document 141.