The largest gathering of free Germans since John F. Kennedy went to Berlin in 1963 turned out in Bonn the other weekend to protest a plan to place new American nuclear missiles in Germany.

The immediate cause of this powerful new tide of sentiment was the plan adopted by the NATO Council two years ago for the placement of 572 land-based mid-range thermonuclear missiles in Western Europe, some 200 of them in West Germany. These missiles are intended as a counter to Soviet deployment of new theater weapons, in particular what the West calls the SS20, a modern, sophisticated mobile missile that can reach all of Western Europe and the Middle East and much of Asia.

According to Secretary of State Alexander Haig, there are already 750 warheads deployed on SS20 launchers, and in his view the SS20 and other new theater systems have "presented the alliance with a threat of a new order of magnitude."

At the end of next month, American and Soviet negotiators will sit down in Geneva to negotiate on the question of the limitation or reduction of those systems and perhaps others that can reach Western Europe or the Soviet Union. This effort is the necessary twin to the plan for missile deployment.

Given the strong European desire to see the proposed American deployment negotiated away, and the widespread belief that the new American administration is unenthusiastic about arms control, there would be considerable danger of a split between Europeans and Americans even if the issues that will be put on the table were simple, and even if the Soviet government were full of eagerness to ensure the unity of NATO.

But because there is indeed a substantial Soviet advantage in the special field of theater-range missiles, and because there is growing division among Europeans over the urgency and desirability of the new American weapons of this class, it will be very easy indeed for Moscow to make proposals that will be unacceptable to the American government and those who agree with it in Europe, but highly appealing to others.

We must go back and see what it is that the proposed new American missiles are supposed to do, how the original intent of the proposal has been lost sight of, and why it is that when carefully considered the proposal is neither necessary nor desirable for the safety of the alliance, unless the nations of Western Europe themselves clearly support it.

The basic premise for the proposed new force was that without it, primarily because of the new effectiveness of the SS20, the Soviet Union would have a new capability for nuclear attack on Europe against which the West required a new and balancing counter. But this basic premise was quite simply wrong. The SS20 did not and does not give the Soviet Union any nuclear capability against Europe alone that it did not have in overflowing measure before a single SS20 was deployed. Not only were the existing SS4s and 5s, though old and cumbersome, entirely adequate in themselves for threatening a nuclear attack on Europe, but what is much more important, every long-range Soviet strategic missile that can reach the United States can also hit Europe. There are so many of these missiles--some 2,500--and they have so many large warheads--some 7,000--that less than 10 percent of the force could produce all the results in Europe that could ever be feared from the SS20.

The underlying reality is that the location, the range, and even the vulnerability of particular weapons systems do not define either the capabilities or the intentions of any nation that, like the Soviet Union and the United States, has built multiple long-range nuclear systems with an enormous redundancy of survivable warheads. For such nations, capabilities remain varied and overwhelming even when whole systems are subtracted (which is why the notion of any early "window of vulnerability" related to the U.S. Minuteman is quite simply inane). Moreover, the capabilities of strategic systems are defined not by the mind-sets of their designers or advocates, nor by the planning processes at staff levels in Omaha or Brussels or Moscow or Washington. Capabilities are defined by what these systems, or parts of them, can actually do if they are so commanded. The ineluctable reality is that long-range systems can hit middle-range targets; they have that capability.

Thus when you have vastly more than "enough" for intercontinental strategic deterrence, as both sides do today, you have more than enough for smaller assignments too. On this quite basic point the simplistic analyses of some nuclear planners, both in NATO and elsewhere, have been deeply misleading to their political superiors.

As with capability so with intent. In a world of strategic nuclear redundancy, political intention is constrained not by the capabilities of particular opposing systems but by the absolutely inescapable risks attendant upon any use of nuclear weapons that might trigger a reply.

No one can be absolutely sure that a major Soviet attack on Western Europe would provoke an American strategic reply--but no one, given the existing levels of American commitment and American troops in place, can possibly be certain that it would not. The certainty of this uncertainty is what deters the men of sanity on both sides; and if it needs some marginal reinforcement in NATO today, that need is mainly in the field of conventional troops and weapons.

With a single important exception, there is nothing the 572 new American warheads can do that cannot be done as well by other systems that we already have or plan to have. Nor does the location of the weapons make any difference from the American standpoint. Whether they are based in Germany, or at sea, or in Nebraska, there will always be the same awful magnitude in any presidential decision to use these weapons against anyone, and in particular against the Soviet Union, whose leaders know as well as we do whose command would send them, and where to direct the reply.

There is indeed one thing some of the new missiles can do that no other weapon can do, but it is something we should not want to be able to do. The Pershing II missiles--there are 108 in the plan--can reach Russia from Germany in five minutes, thus producing a new possibility of a super-sudden first strike --even on Moscow itself. That is too fast. We would not like it if a Soviet forward deployment of submarines should create a similar standing threat to Washington. It is not for us to be the ones who first put the decapitation of the great rival government on a hair trigger. It is deeply in the general interest of all that neither side should pose such threats to the other.

There remains one important argument for the ground-launched cruise missiles: our allies may in fact want them. These at least are not plausible first-strike weapons because they move at less than the speed of sound, and they can reasonably be seen as replacements for theater-based aircraft less able to reach their NATO targets than they once were. We should not hold back on this part of the agreed deployment if that is indeed the settled will of our European allies. But neither should we make the acceptance of these weapons a test of loyalty to the alliance.

If we must not presume to decide this question for our friends, neither should we presume that it is decided by a single rally in Bonn, however large and well-organized. The Europeans who have supported the new deployment are neither few nor feeble; and the agreement of 1979 is not to be abandoned if indeed this new force, with the Pershing II modified or omitted, is still wanted by Europeans. But it would be all wrong for Americans to use the advantages of ownership to press for a single solution when there are many to choose from. We must think in terms of what Europe wants and needs, a ind not in those of a mechanical matching of every Soviet move.