Where the Russians are vulnerable

Westerners consume a steady flow of statistics comparing United States and Soviet military hardware, manpower, and nuclear weapons capabilities. War, however, puts more than data and hardware to the test. The full range of a nation's political, economic, as well as military strength is put into play.

One of the least examined elements in the Soviet-American balance of power is Soviet vulnerability to political fragmentation. Both official and popular Western images of the Soviet Union fail to recognize the multinational character of the Soviet state. Ethnic Russian domination of the Communist Party contributes to the widely held perception that ''Russia'' and the ''Soviet Union'' are synonymous.

Ethnic Russians comprise barely 50 percent of the Soviet population. They are concentrated in the west central part of the country and are buffered from neighboring countries by 14 union republics of the USSR populated predominately by non-Russian ethnic groups.

Russian control of these peoples and their lands began more than five centuries ago under the leadership of the great Tsars. The steady expansion was, in part, prompted by a lack of natural defensive frontiers in a world of hostile neighbors who repeatedly invaded and subjugated the smaller Russian state.

Most of these conquered areas attempted to break away during the Russian revolution, but were reconquered by the new Bolshevik government. Those that did manage to gain their independence, such as the Baltic states of Latvia, Lithuania, and Estonia, were reincorporated during World War II.

Maintenance of this multinational empire and Russian perception of their security became and remains synonymous. Under Marxist-Leninism the solidarity of the working class and economic prosperity were to have disposed of narrower national and ethnic loyalties. But the ideological melting pot has failed to integrate the non-Russian peoples except for the Belorussians, who are closely akin. They remain fiercely nationalistic, under control for the time being, but in crisis or difficult times pose for the Russian leadership the prospect of latent opposition and hostility.

The apprehension that Russians feel toward their nationalities is reflected in the Communist Party structure, state bureaucracies, the armed forces, and the secret police. Each is dominated by ethnic Russians including the large Soviet Army where non-Russians are trusted in large numbers only in construction or supporting units, and, even then, must serve outside their native territories.

Maintaining the empire poses serious problems for Soviet foreign policy over the long term. Challenges in Eastern Europe could eventually spill over into neighboring Soviet republics. Islamic revolutions in Iran and Afghanistan could affect the loyalties of 40 million Soviet Islamic citizens in Central Asia. If set in motion by a major crisis, the pressures of nationalism could set all of the Soviets' ethnic dominoes falling out of control.

Internal political problems combined with current Soviet economic disasters will make it considerably more difficult and possibly less attractive for Soviet leaders to project their power in the third world. They do so at the increased risk of neglecting their empire at home.

This is the fragile political base for Soviet military power. Greater emphasis on these vulnerabilities and fewer alarms over their military prowess would strengthen US strategy around the globe.