The Defense Department defended the new U.S. nuclear war strategy yesterday as an evolutionary rather than a revolutionary change, and said the State Department was fully informed in the lengthy process of its development.

The Pentagon viewpoint was made public after news reports of Secretary of State Edmund S. Muskie's unhappiness that he knew little about the new doctrine before accounts of it were published n last Wednesday's editions of The Washington Post and The New York Times. Muskie expresed his concern to reporters late Friday night as he returned from a speaking tour on the West Coast.

White House press secretary Jody Powell said yesterday that Policy decision was not so significant that it merited Muskie's involvement. He said Muskie probably would not have been upset had he known that the decision was not itself a major new change in policy, but was a step to implement a policy change previously decided.

"It was not a decision that normally passes through or involves the Department of State," Powell told the Associated Press. "The Department of State has been involved and was involved in that process" of reaching the basic policy decision.

Furthermore, said Powell, Muskie missed two opportunities to find out about the decision -- before it became public knowledge -- because he was traveling.

According to the Pentagon account, the history of the new doctrine in the Carter administration goes back to a 1977 directive by President Carter calling for a "nuclear targeting policy review" to be undertaken by the Defense Department.

Secretary of Defense Harold Brown completed that review in November 1978, after which "extensive interagency review and coordination at a high policy level" was conducted on the plan from mid-1978 to early 1980, according to the Pentagon account. This review is said to have involved a half dozen or more meetings attended by representatives of the State Department and the Arms Control and Disarmanent Agency.

According to Pentagon and State Department officials, the policy review meeting took place before Muskie replaced Cyrus R. Vance as secretary of state May 8.It was unclear why Muskie had not been briefed on the matter in the past three months.

Brown, in a message sent Friday to defense ministers of North Atlantic Treaty Organization members and made public yesterday, said the U.S. strategy is "designed to enhance deterrence of any Soviet action that could lead to nuclear war by making clear that we have both capabilities and plans for use of our forces, if deterrence fails."

Pentagon officials depicted the nuclear strategy, formally adopted several weeks ago on Carter's orders, as the culination of evolutionary changes beginning under then-secretary of defense James R. Schlesinger in 1974.

In general, the new doctrine reportedly shifts the emphasis of U.S. strategic nuclear weapons aimed at the Soviet Union from population centers to military targets and control centers. Such a strategy would make possible at least in theory, a nuclear exchange short of total war.

In his message to NATO, Brown said that "it is crucial that the Soviet leadership recognize that by aggression they would risk not only a general U.S. retaliation on the full range of targets; they must also understand that if they choose some intermediate level of escalation the United States could by more limited response, impose on the Soviets an unacceptably high cost in terms of what the Soviet leadership values most -- political and military control, military power both nuclear and conventional and the industrial capacity on sustain military operations."

Brown added, "We have no desire to fight a nuclear war; it would be an umimaginable catastrophe. . . . But the surest way to avoid such a war is to make certain that the Soviet leadership can have no illusions about what such a war would mean for Soviet state power."

A senior Pentagon official said Brown had intended to make the newly adopted nuclear plans public in an address to the Naval War College Aug. 20. The official said Brown had planned to brief Muskie in detail before that speech.