Why the Russians might -- or might not -- be tempted by Nicaragua

The statement by Soviet President Brezhnev on the possibility of placing Soviet nuclear missiles close to US shores if the United States continues to deploy its missiles in Europe highlights the strategic importance of the Caribbean and Central America. While most observers immediately associated the Russian threat with a repetition of the 1962 Cuban missile crisis, a more ominous and dangerous scenario may be developing. It is possible that Brezhnev was referring to a deployment of Soviet nuclear capability not in Cuba but in Nicaragua.

The use of a Nicaraguan Pacific port for Soviet nuclear submarines would bypass the US-Soviet ''understanding'' of 1962 which pledges the Kremlin not to introduce ''offensive'' weapons into Cuba. The Soviets have made no similar pledges regarding Nicaragua. This would pose significant problems for the US and could lead to a Soviet-American crisis.

So far Moscow has been cautious in its support of the Nicaraguan government. The Kremlin leaders may be concerned about increasing US apprehensions over the possibility of another Cuba. The Soviets, furthermore, don't seem eager to embark on large-scale support of regimes that are not totally controlled by loyal Marxists. Soviet experience with regimes that gain power without Soviet support has shown that these regimes sometimes pursue policy lines independent from Moscow and are difficult to control.

The possible strategic advantages for the Soviet Union of mounting a military presence (naval as well as air) in the Pacific side of Central America based in Nicaragua might be significant. It would facilitate the deployment of Soviet submarines off the Pacific coast of the US, as well as extend the time these submarines can remain on station and shorten the transit time to and from their bases. It might generate a threat to US SAC (Strategic Air Command) bases located in the southwestern US. It would complicate the US ASW (antisubmarine warfare) problems and possibly reduce the risks of an early US intercept of Soviet submarines leaving their bases in the Soviet Union. It might allow the Soviet navy to keep better surveillance over movements of US submarines and other naval vessels in the Pacific ocean. And finally, an improved Soviet submarine and naval deployment might be critical to a Soviet preemptive strike posture in accordance with Soviet military doctrine.

The use of Nicaraguan ports by Soviet submarines is not likely to result in a major shift in the East-West strategic balance, nor critically alter the effectiveness of the US strategic deterrence posture. Yet, if successful in establishing this presence, there is no reason to believe that the Soviets would limit these activities to Nicaragua. Conceivably the Soviet Union could attempt in time to introduce other strategic ''offensive'' weapons into Nicaragua as it did in Cuba in 1962. Furthermore, if successful in Nicaragua, the Soviets might attempt to use other Central or Latin American ports for similar purposes.

It is not totally clear what the Sandinistas might hope to gain from such developments. They might perceive that the presence of Soviet naval forces based in Nicaragua would constitute an informal guarantee of Nicaragua's internal and external security. Faced with mounting attacks by the US government they may hope to deter a possible US intervention and discourage covert operations against the Nicaraguan revolution.

It should be pointed out that an increased Soviet presence in Nicaragua might frighten some Central American nations and thus have the effect of weakening rather than strengthening possible Soviet appeal and influence in the area. As the 1962 missile crisis showed, most Latin American nations perceived Soviet actions in Cuba as a threat to hemispheric security and rallied behind the US. It is likely that a similar although not as unanimous reaction would develop now were the Soviets to establish a presence in Central America.

In view of the fact that the US-Soviet global competition involves to a large degree image-building by both sides, US policies must be careful to avoid actions which may help magnify the significance of Soviet successes or to establish positions which may merely allow Moscow to violate them - which in turn could lead to a weakening of US credibility and prestige.