During the 1962 Cuban missile crisis, President Kennedy asked Charles E. Bohlen, his Soviet-affairs adviser, why the Russians were pushing the confrontation all the way to the brink of war.

Bohlen responded: "I suspect that they are simply following one of the old edicts from Lenin: "Thrust in the bayonet until it strikes steel.'"

The phrase caught Kennedy's imagination and helped crystalize his thinking about how to respond to the Kremlin. In the end, the Soviet bayonet did strike steel, and the Russians, in keeping with Lenin's precept, pulled back. Ever since, it has been a cardinal principle of Soviet foreign policy to avoid getting into any military situation that might end in a confrontation with the United States. Instead, Cuban hands guided by Russians are thrusting by bayonets into the world's soft underbelly, where they are not likely to strike steel.

As a guide to Soviet intentions, that particular Lenin maxim may be an oversimplification. But Bohlen was a pragmatist when it came to Soviet affairs, prefering always to deal with realities. For him, the Lenin statement was good enough to explain what was behind the Cuban missile crisis, and it goes a long way toward explaining present Soviet interventionist policies in Africa and elsewhere.

In the 15 years since the Cuban crisis, Soviet policy has followed two parallel tracks. The first has been the avid pursuit of detente with Europe and the Atlantic Alliance, with the primary aim of avoiding confrontation where it might involve striking steel. This process began almost immediately after the Cuban crisis, when Nikita Khrushchev accepted Kennedy's proposal for a nuclear test-bana treaty. It has continued through the first strategic arms limitation agreement, the Helsinki agreements on security and cooperation in Europe, the Vienna talks on mutual force reduction and all the ancillary talks going on with the Carter administration. From a Soviet standpoint, all of these serve to reduce the likelihood of a superpower confrontation and permit the Soviet Union to level off in parity with the United States.

The second aspect of Soviet policy is opportunist, expansionist and interventionist, involving in Lenin's terms the leadership of world revolution. Wile pursuing detente to avoid having to strike steel, the Kremlin has kept its orthodox Marxist-Leninist theoreticians and its militarists happy by building the largest Navy in the world, modernizing and re-equipping Soviet ground forces, bringing certain of the Warsaw Pact allies under firmer control and building up an air-lift and sealift capacity that gives the Soviet Union the capability to intervene military on a global scale.

The Russians, in other words, enjoy the same kind of capability that the United States has had for the last 30 years. And the Russians have the added advantage of being able to command their Cuban Afrika Korps - along with the East German secret police and the Czechoslovakian arms technicians - to do the dirty work of intervention.

No communist ideological excuse is needed for intervention. In the post-war days into the 1960s, when the Stanlin and khrushchev were constantly ranting against containment, it was a rule of thumb that the Soviets were not going to waste power or money except in support of communist movements.

That is no longer so. The Kremlin technique now is to send in the power, then find the communists afterward. There need not be any kind of communist early-warning system in the form of revolutionary movements proclaiming a class struggle and then being rewarded with Moscow's help. The motto of 19the-century imperialism was that trade follows the flag; the motto of 20th-century Soviet imperialism seems to be that ideology follows power.

From Lenin to Stalin to Khrushchev to Brezhnev, the expansionist, neo-imperialist Soviet policy has been consistent.

In the early post-revolutionary days it was enough for the Red regime simply to digest and consolidate itself within its borders. World War II provided an opportunity to extend Soviet imperialism to the Baltic states and across Eastern Europe to the Elbe. A combination of the Cuban crisis and the Berlin Wall brought expansion in that direction to an end. Now Soviet power has been readied for a new phase of imperialist ventures at great distance from the Soviet perimeter.

George F. Kennan writes in total disillusionment today of his containment policy of 30 years ago. he mentions "a certain melancholy notoriety which has dogged my footsteps ever since like a faithful but unwanted and somewhat embarrassing animal."

Other Kremlinologists see in this new geopolitical leapfrogging that Moscow is directing across Africa - now in Afghanistan, maybe next in Iran or across the Red Sea to Saudi Arabia - a potential tilt in global strategic patterns of far graver consequence to American interests than were faced in either Berlin or Cuba.

The problem is the same for President Carter as it was for presidents Truman, Eisenhower, Kennedy, Johnson and Nixon: How do you ensure that the bayonet will strike steel?"