There is little doubt that the Reagan defense budget is in for serious trouble. This can come from a number of sources--supporters of underfunded social programs, opponents of massive federal deficits and critics of the ways in which the administration proposes to use the money in reviving our military power. If disastrous cuts are to be avoided, there is a pressing need for a better understanding in Congress and by the public of not only what the proposed budget will do for the Armed Forces but also what cuts in the budget will do to them and what the effect on national security would be in both cases.

No such understanding is likely to be reached under current budget procedures--a statement applicable to all budgets I have known, beginning with the Eisenhower administration. Normally, spokesmen appearing before congressional committees may be expected to explain and defend the budget largely in terms of major service (Army, Navy, Air Force, Marine) programs, with emphasis on those with the biggest price tags. Usually, they will argue that the funds are needed:

* As an annual installment on a multi-year program previously approved by Congress;

* To replace some major weapons system that has become obsolete--for example, the B1 bomber in replacement of the B52;.

* To provide a new weapon or more old ones to equal or surpass the Russians in quality or quantity, as in the case of the MX missile;

* To exploit a scientific breakthrough that may permit the development of something completely new in future warfare--space weapons, for example.

In the past, the responsible congressional committees have usuly argued at length over these individual programs, approving funds for some and reducing or eliminating funds for others. At no time have I known of a concerted effort to evaluate the aggregate of all programs to determine the operational adequacy of the forces generated by them to carry out a military strategy based upon the anticipated needs of the national policy for armed support.

Congress should insist on receiving such an evaluation prior to action on future budgets. If time makes it impossible for this year, it should be on the agenda for the next year.

Let me outline the kind of operational appraisal I think Congress needs. To begin with, it should set forth the administration view of the dangers to our national policy and global interests that are likely to require military force to prevent, forestall or defeat them. Although probably far from the official view, for present purposes I would propose the following list: the perennial malevolence of the Soviet Union and its growing military strength; the weakness of the NATO allies and their exposure to aggression in various forms; the perpetual trouble potential in the Middle East-Persian Gulf region; and the growing vulnerability of the American economy to its ever increasing dependence on foreign imports.

With the major threats identified, Congress would need to know the size, composition and readiness of the forces that the president and his advisers consider necessary to cope with these threats (at least in their initial stages) and the specific tasks the forces should be prepared to perform. Again, in the absence of official guidance, I suggest the following as the basic tasks against which to measure force sufficiency:

A. The protection of the North America- Caribbean region and air-sea approaches.

B. The deterrence of nuclear war with the Soviet Union.

C. The fulfillment of our military obligations to NATO.

D. The maintenance of a military presence in the Persian Gulf region in consonance with the requirements of the Carter Doctrine.

E. A strategic reserve for use in ensuring access to essential overseas markets, in reinforcing overseas garrisons and in dealing with unpredictable contingencies in the Third World.

Except for Task B, existing forces could be earmarked as necessary for more than one task, but with an indicated priority of task readiness. "Task readiness," as used here, should be understood to mean more than just the unit readiness of each component of a task force: it must also include the readiness of the air-sea transport required for moving the task force to its overseas destination and of a follow-on supply line that would ensure timely arrival of the supplies and replacements essential for sustained combat.

The "bottom line" of the appraisal would be a summary of the present forces available for the foregoing tasks, their present adequacy and readiness for those tasks as judged by the Joint Chiefs of Staff and the contribution to improving their readiness expected from the recommended budget.

In questioning the officials presenting the appraisal, the congressmen would have an opportunity to probe for the genuine goals of the Reagan military policy as opposed to rhetorical statements for political effect. An initial question might be whether Secretary of Defense Caspar Weinberger's recent annual report to Congress is intended to convey the important changes in military policy that commentators at home and abroad are reading into it.

Each of the five tasks contains implications requiring questions for illumination. Under Task A, it would be well to know the kind of bomber defense that is planned and how civil defense will be regarded. Under B, how will deterrent sufficiency be determined for our strategic forces? In the case of C, what is the assumption as to our ability to reinforce our NATO allies once a major attack is under way? In plans for the Persian Gulf region, what will be the mission of the forces assigned-- merely to fly the flag, to serve as a moderately strong tripwire with some deterrent value or to act as a stick-it-out advance guard to be reinforced from the United States as rapidly as possible? Under E, one must inquire as to the identity of the essential markets and how the Armed Forces might be employed to ensure access to them.

One would expect that, after listening to such a presentation by the senior spokesmen of the Defense Department and with ample time to cross-examine them, an attentive congressman would have a pretty good idea of what the Pentagon will do with the resources provided by the budget and the adequacy of the forces generated to do the jobs expected of them. He should also have a good notion as to the essentiality of the contribution to task readiness of controversial weapons systems such as the MX, the B1, the Navy supercarriers and the new Army tank. If ever a budget-cutter before, he should know better where the fat is to be found for excision and the muscle for preservation--traditionally the alleged purpose of such surgery. If the above expectations were realized, the added burden placed on the Pentagon in preparing the appraisal would be more than justified.

Indeed, it would be justified in its own right. For the first time in memory, our national leaders would have been obliged to produce something resembling a military policy consistent with the needs of national policy. Further, the military forces would have been assigned specific essential tasks, with this adequacy determined by task readiness, not by some numerical relation to Soviet forces. All this would be quite an accomplishment.