THERE IS a strange, even chilling, split-screen aspect to the war talk filling the air these days. At one level it is all theory and scenario--that is, play. At another it is all blood and danger of worse to come. At the NATO meeting in Bonn, the discussion was couched in the esoteric calculus of the great alliances' forces and the possibilities of carefully calibrated reductions. In the newspapers, it is large-scale maps with curved arrows illustrating grand strategy, suggesting large and serious games. On the ground, it is the real thing and a good deal less tidy--in the Falklands, in southern Lebanon, on the border between Iraq and Iran. The three small wars have become an unintended commentary on the great questions of arms and arms control as NATO cautiously debates them.

The present tacit rule seems to be that wars are tolerable in proportion to their distance from us--that is, from us North Americans and Europeans. In northern European politics, the peace movement currently holds the high ground, and Mr. Reagan is moving, with speed and some considerable skill, to address it. Elsewhere, other views about warfare prevail. Much of the peace movement persists in its historical error of assuming that simply banning the weapons can somehow exorcise the inclination to resort to war. And yet weapons cannot only make combat feasible and in some situations much more likely. They can also generate a certain inclination to let others try them out. Each of the small wars has an attentive audience of specialists most eager to see how the new technologies work in actual practice.

Americans and other arms suppliers cannot take much gratification in watching the present uses of the weapons that they have built and sold to the world, from the attack aircraft in Argentina to the tanks in Iran and the missiles just about everywhere. But as the small wars end, the American government and, no doubt, the others will again feel that familiar temptation to try to repair their relations with everyone, both winners and losers, with new sales of arms in more effective models. Arms sales have become the universal token of esteem, and the most sincere expression of best wishes for a speedy recovery.

The three small wars are at least serving the purpose of demonstrating, most graphically, the important truth that war is, by its nature, profoundly unpredictable and the risks are always far higher than the experts claim. Despite the superior performance of the British forces, and the tough talk in London, it is hard to believe that the British government would have sent the navy if it had really expected to lose six ships. The Iraqis, who started the war with Iran, did not expect to find themselves fighting on their own soil. As for Lebanon, it is the looming possibility of further surprises that makes the collisions there particularly alarming.

The three small wars, each of them extraordinarily destructive, furnish a useful reminder of the nature of the subject under debate in NATO. The force levels are not merely numbers on a sheet of paper. In Europe, where the most sensitive and dangerous of all the borders run, forces can safely be reduced only when they are reduced on both sides simultaneously. But Mr. Reagan, over the past eight months and notably this week in Bonn, was utterly correct to declare the strong American interest in negotiating arms reductions. The central effort has to be directed to the strategic arms, and the U.S.- Soviet equation. But, as the three small wars suggest, the principle has broader applications.