AT A TIME when there is a tendency to revert to simplistic thinking about non-nuclear wars, unconcernedly dismissing all mention of Vietnam or even Korea, where some 40,000 Americans are still stationed, this book is a timely reminder of the illusions and futility that brought the United States into those two catastrophic conflicts.

From the vantage point of a White House reporter, National Book Award winner Robert Donovan captures the complexities of decision-making with their concomitant implications, intrigues, undercurrents and pressures. He incisively examines the origins and conduct of both wars and finds striking parallels in their anatomy, concluding that they were "cut from the same cloth of the policy of containment of communism in Asia."

Nemesis is an excellent study in tandem of both wars and of the devastating effect they had on the lives of presidents Truman and Johnson. It skillfully and unambiguously compares the causes and effects, the pressures and commitments, the traps and pitfalls that led to tragic and inconclusive results.

Donovan introduces Truman and Johnson as "two gamecocks who had come to the White House originally upon the death of two famous presidents" and who later "had been elected in their own right to show what they could do." Their elections, 16 years apart, were hailed as harbingers of progress in civil rights and rededication to the policy of using federal money to improve the lives of the American people. But the Truman Fair Deal and the Johnson Great Society became mired in conflicting interests that had roots in their predecessors' legacy -- containment of Communism.

This legacy, Donovan suggests, governed the role and conduct of both presidents, casting a pall over their administrations, shattering their dreams for a better society, and compelling them to leave Washington with a deep sense of unfulfillment. Neither president was able to end the war in which he had committed American troops to combat.

Donovan credits President Truman with having "established the framework in which all the postwar presidents, including Johnson, shaped their own (foreign) policies," and so it was. President Roosevelt had advocated a system of postwar trusteeships for dependencies such as Korea and Indochina (Vietnam). Truman subscribed to that concept and his immediate concern was control of Korea, bringing the United States into competition with the Soviet Union. In China the Nationalists were losing ground to Mao Tse-tung, and in Vietnam the French were faring no better against Ho Chi Minh. In Southeast Asia leftist elements clamored for independence. In the Middle East and in Europe local communist parties maneuvered for political control. The anti-communist hysteria was on and in 1948 the Soviet Union became the enemy.

Nemesis is rich with anecdotes about the two presidents and the men around them. "Have to talk to God's right hand man . . . " Truman wrote to his cousin on the way to meet with MacArthur on Wake Island. When the president's plane arrived, the general was sitting in a Jeep surrounded by a small crowd, seemingly trying to upstage Truman, and did not go out to the ramp. The president "refused to budge from his seat until MacArthur finally came to the ramp . . . .Only then did he descend . . . "

JOHNSON's last years in office were difficult ones. Reverses in Vietnam, public dissent, a party split, and Bobby Kennedy's making a run for the presidency disheartened Johnson. "Sometimes in those months Johnson, who was not a regular communicant in any church, be=came so consumed with anxiety that late at night he would order his limousine and a Secret Service detail and drive to St. Dominic's Catholic Church . . . for private prayers with a few priests and Christian brothers . . . .Beginning in 1966, he returned for consolation from time to time, including a night when he had ordered the bombing . . . near Hanoi and Haiphong."

Donovan's inquisitive style raises many questions. Particularly troubling is the abysmal lack of, or appreciation for, intelligence at the policy and decision-making level prior to committing our nation to war. Days before the North Koreans invaded South Korea none of Truman's advisors had told him of massive preparations north of the 38th parallel for a drive south. General Omar Bradley, chairman of the Joint Chiefs of Staff, later said, "I don't think you can say that any of us knew . . . when we went into this thing, what would be involved." And Donovan points up that during the MacArthur offen=ive in Korea, "The crowning mischief was that no American official had the slightest valid idea how many Chinese might be in Korea." Further on he notes "The lack of intelligence itself became an incentive for advancing."

The same conditions prevailed in the Vietnam conflict. "Neither Johnson nor Eisenhower nor Truman nor Acheson nor Dulles," says Donovan, "had ever really understood Vietnam, its people, its culture, its history, its institutions, its politics, its aspirations."

Nemesis makes good reading. It is terse, factual, well-documented, devoid of over- burdensome details and thorough in essentials.