Washington — In developing a global strategy for superpower military forces, one inevitably enters ''the world of assumptions, scenarios, and hypothetical projections,'' as White House national security adviser -William Clark said in a recent speech.
But there are also the practical considerations that any administration must deal with: politics at home, relations with friends abroad, and the relative strengths and weaknesses of the perceived enemy.
The Reagan administration is now at this point where theory and practicality converge.
The White House is digging in (and positioning itself for acceptable adjustments) on an unprecedented peacetime military buildup - for which public support is softening. Top US officials, including President Reagan, are about to leave for defense and economic discussions with the European allies. The White House must reevaluate its strategic actions in light of new information on the military and economic strength of the Soviet Union.
In a speech at Georgetown University last Friday Mr. Clark was articulating and clarifying a refined version of national security strategy that has been emerging over the past several months.
Early on, the administration rejected the notion that conventional conflicts would be limited to a ''two war'' or ''one-and-a-half-war'' scenario or that such engagements would likely be short-lived.
''Such mechanistic assumptions,'' Defense Secretary Caspar W. Weinberger wrote in this year's posture statement, ''neglect both the risks and the opportunities that we might confront.''
This has not changed, for as Clark said last week, ''any conflict with the Soviet Union could expand to global dimensions.'' Also still in place is Mr. Weinberger's position that the US should be able to pick and choose where it will fight if forced to. Or as Clark said, ''The capability for counteroffensives on other fronts is an essential element of our strategy. . . ''
But here, the practicalities enter in. Because of economic constraints here and in Western Europe, administration officials now admit they could not confront the Soviet Union on all fronts simultaneously in the event of conflict.
''Looking at our resources and the global aspects of what could occur in the event of confrontation, we simply don't have the abilities to meet them on every front,'' said a high administration official. ''We are going to have to look at priorities.''
Growing concern about allied strength is part of this realization.
''The current stresses in NATO couldn't come at a worse time,'' former Defense Undersecretary Robert Komer told a congressional subcommittee last week. ''Given the relative decline of US power, we need our allies more than ever - as much as they need us.''
In its talks with NATO leaders next month, as well as in formulating military strategy, the administration must contend not only with increased allied nervousness over the threat of war. It also must deal with growing restiveness on Capitol Hill about US commitments to the defense of Western Europe.
It is frequently noted that NATO (unlike the Warsaw Pact) is a voluntary association of relatively rich countries. When the defense spending of such non-NATO allies as Japan, Spain, and Korea is added in, the allies outspend the Warsaw Pact by clear margins. Because of their independence, however, NATO countries have not chosen (or been forced) to closely integrate their military forces. Because of ''wasteful overlap and duplication,'' says Mr. Komer, ''NATO as a whole is less than the sum of its parts.''
The Pentagon has estimated that as much as 40 percent of NATO's military investment represents duplication, compared with only about 10 percent for Warsaw Pact countries.
In clear recognition of this, the US Senate in a near-unanimous vote recently urged the North Atlantic alliance to pool its financial, technological, and manpower resources to provide a more effective and efficient common defense.
In presenting its national security strategy, the administration is addressing two audiences: Congress, which has yet not reduced in any significant way the Pentagon budget; and the European allies, who may see this as a softer-toned if not more acceptable base upon which to discuss mutual allied aims.
Many in Congress (including such relative hawks as Sen. Sam Nunn (D) of Georgia) worry that the adminitration's military goals could be far more costly than the $1.6 trillion defense spending plan outlined for the next five years. If the administration indeed is lowering its sights, these concerns may be allayed at least somewhat.
Whether the fears of many Western Europeans are similarly allayed remains to be seen. It may be undeserved, but Mr. Reagan still projects a militaristic image for many.
Just as they are rethinking their policies in light of congressional and allied concerns, administration strategists also must adjust the steps they take to implement policies as new information about Soviet military and economic capabilities emerges.
In a series of recent reports based on interviews with former Soviet military men now living in the United States, Rep. Les Aspin (D) of Wisconsin (a former Pentagon analyst) detailed numerous problems with Soviet military manpower and weapons.
A recent report in the Soviet military newspaper Red Star confirmed that there have been problems with the quality of military recruits and the ability to attract sufficient officer candidates.