IT IS A telling sign of the rush of events that the new Soviet-American accord on reducing conventional arms in Europe was received with something of a yawn. This is the issue -- building down the largest, longest, most menacing face-off of armies in the world -- that confounded negotiators of East and West for years. Yet when the new tentative agreement in principle was announced, it seemed anticlimactic. The ideological and political tensions that supplied the Cold War's defining sense of confrontation and danger had already faded. Political and budgetary pressures in both West Europe and East Europe already ensure that even the reduced weapons ceilings are higher than the levels the public cares to bear. One party to the face-off, the Warsaw Pact, is a memory, and the other, NATO, is searching for a purpose "beyond containment." Nothing better indicates the reigning topsy-turviness than that Soviet troops in what was until Wednesday East Germany are now on the payroll of a NATO member, the Federal Republic of Germany.

And yet there is a demonstrable need for armies of a certain size and shape to be maintained. This creates in turn a further need for the shrinking to be done in an organized, negotiated way that adds order and trust to a process that might otherwise be random and even destabilizing. If in earlier times the purpose of arms control was to manage tension across the East-West divide at lower levels of risk and cost, then the purpose of arms control now in Europe is to support the continent's marvelous reach across that divide. How appropriate that the new agreement was reached on the day Germany was unified: just the right match of military relaxation and political healing.

The agreement sets in treaty concrete Mikhail Gorbachev's breakthrough principle that the Soviet Union, having greater forces, must accept unequal (greater) reductions. Where some of the new ceilings actually exceed the levels of forces that NATO has in place, the Kremlin is either destroying or withdrawing from the treaty's European area tens of thousands of the machines of war. The new figures are lower and unthreatening. With them come confidence-building verification measures and arrangements for monitoring future deployments and maneuvers. The result extends the warning time of a theoretical Soviet attack from days to years. All these matters become the necessary military underpinning of the new Europe.