WHEN Fiorello La Guardia read the comics aloud over radio to New York children during a newspaper strike, one of his lieutenants was distressed: the mayor would thenceforth be remembered not as a leader of gravity and purpose but as the Man Who Read the Funny Papers.

Harry Truman also risks assignment to the comic opera of American history. The famous profane protest to the critic of this newspaper who disliked his daughter's singing, the morning "constitutionals," the smiling pledges to "give 'em hell," the piano playing and the Hawaiian shirts -- these colorful lineaments of a singular personality have done much to conceal the homme serieux.

No one has done more to rescue the 33rd president from the historical music hall than Robert Donovan. His Conflict and Crisis (1977) treated the first four years of the Truman administration -- the beginning of the Cold War, the reform program of the Fair Deal, European reconstruction and the founding of Israel, the legendary political comeback of 1948.

Tumultuous Years covers the second Truman term with the balance, comprehensiveness and economy characteristic of the earlier volume. Still, this is a more ambitious book, for it is almost entirely devoted to the conditions and events -- the international context, the domestic constraints and opportunities, the devising and enactment of strategy -- that shaped American foreign policy during those years.

By 1949, the Fair Deal was mainly out of steam. Like other reelected presidents unaccompanied by strong majorities in Congress, Harry Truman was deadlocked on Capitol Hill. The congressional resistance was composed of Southern Democrats who had bolted the 1948 convention, other party members who had never much warmed to Truman as president, and Republicans who -- with Thomas Dewey's defeat snatched from the jaws of victory -- were frustrated, bitter, and vengeful. Reforms proposed by Truman, such as Medicare, expanded public housing and Social Security benefits, and voting rights, awaited future Democratic presidents for passage.

The silver lining in this cloud was that it enabled Truman to concentrate on foreign affairs. It can be fairly argued that the second term presented a more awesome challenge than the first. Despite the hazards of leading the nation through the early Cold War to a permanent commitment to collective security, the president had enjoyed advantages that were now vanishing. By 1949, the Soviets were equipped to end the American monopoly on atomic weapons; Mao's armies were poised to seize China and rob America of the linchpin of its security system in Asia; the bipartisan consensus behind American foreign policy was eroding.

As Donovan suggests, the foreign policy of the first term was based on a dangerous contradiction. On the one hand, Truman exalted military strength as the safeguard of peace and assumed extensive obligations requiring the possible use of force; on the other, he cut American conventional force strength from 12 million troops in 1945 to 1.5 million two years later, relying largely on the American atomic monopoly for the security of the West. Threats abroad were resisted principally with such political and economic devices as the Marshall Plan, aid to China and the Truman Doctrine. The founding of NATO brought America into the world to stay.

By 1949, the budget was balanced, employment high, prices steady, interest rates low and strikes minimal. The price of all of this was the withering of the American military. Donovan doubts that Truman squarely confronted the strategic problem of such heavy reliance on the atomic monopoly and proposes that he was dangerously underbriefed. In September 1949 came the great shock: a Soviet atomic explosion, more than a year earlier than expected. "This is now a different world," wrote Senator Arthur Vandenberg.

To cope with the different world, Truman approved the document known as NSC 68, authorizing massive rearmament against the Soviet "design for world domination," as well as the trebling of the defense budget and the building of a hydrogen bomb.

In October 1949, Mao Tse-tung proclaimed the People's Republic of China. Truman's advisers expected to recognize the new government at a politically propitious time -- probably after the 1950 midterm elections. As Donovan notes, this undervalued the symbolic importance of the China issue, especially for Republicans who had long charged the Democrats with overattention to Europe at the expense of Asia.

The cries of "Who lost China?" harmonized with rising anti-Communism that, says Donovan, was not free of Truman's influence. He had whipped up anti-Russian sentiment in order to pass the Marshall Plan and Truman Doctrine and enacted the loyalty program of 1947 to remain on the safe side of the issue. He underestimated the troublesome impact of the Alger Hiss case and of Joseph McCarthy of Wisconsin, "just a ballyhoo artist who has to cover up his shortcomings by wild charges."

Truman's dispatch of American forces to Korea in response to the invasion from the North has been much debated. South Korea had been excluded by both Secretary of State Dean Acheson and General Douglas MacArthur from the American defense perimeter, and the United States had withdrawn its troops there to make better use of them elsewhere.

"It was Truman's nature to respond to challenge," writes Donovan. "An affront to his country and to himself, especially one that struck him as wrong, uncapped his ample reserves of anger and righteous indignation. Furthermore, he had an appetite, too much of a one, really, for unhesitating decision. In the crisis of the sort that had exploded in Asia, subtleties were not his strong suit."

Korea also provided the nation with a showcase example of the need for NSC 68 and an opportunity to show that the Democrats could stand up to Communism in Asia. When Truman stationed the Seventh Fleet in the Formosan Strait two days after the invasion, he thrust America back into the Chinese civil war from which he and Acheson had been working to extricate themselves. Republican support for Truman's actions in Korea was purchased at the price of a full generation of hostility between Washington and Peking.

Of equal moment was Truman's refusal to seek congressional approval for the sending of ground forces to Korea, which Donovan accounts a mistake: "It was the political considerations that counted in what was rapidly developing into a major undeclared war in Korea. The political rather than the legal aspect of war without congressional approval was to hurt Truman, to make the prosecution of the war more difficult for him, and to cause future public concern about what was to be called the 'imperial presidency.' "

The president and his commanding general in Korea, though they had never met, had long been privately contemptuous toward each other. To Truman, MacArthur was a rambunctious faker -- "God's right-hand man"; to MacArthur, Truman was dangerously beyond his depth. Nonetheless, the two men agreed on Korean strategy through the fall and chatted amiably in the only meeting of their lives on Wake Island in October 1950. That month, the full invasion of the North began. Then came the startling entry of the Chinese into the conflict, the routing of American troops, and MacArthur's loud demands for reinforcements and authority to attack Chinese territory.

"Probably no major decision that Harry Truman made in nearly eight years in office is more generally upheld by posterity than his relief of MacArthur," writes Donovan. "By the millions, however, his contemporaries loathed the president for his decision, excoriated him or turned their backs on him for what he had done to a national hero whose objective was the defeat of communism." The melodrama of MacArthur's return and his speech to Congress increased national opposition to Truman's restraint toward China and his persistence in fighting a limited war. Yet it neither changed the direction of American foreign policy nor crippled Truman's leadership.

Truman ended his second term with a whimper. The Korean conflict remained in stalemate. Congressional antipathy to the White House was strengthened by Republican gains in the 1950 elections. Nagging scandals such as the "five-percenter" and "deep-freeze" episodes gave the Republicans ammunition for the 1952 campaign. Truman pressed presidential power to new lengths by seizing the steel industry in April 1952 when it was threatened by a strike that could have injured the war effort; the seizure, privately encouraged by Truman's old friend and poker partner, Chief Justice Fred Vinson, brought 14 separate congressional resolutions for the president's impeachment.

Still as Donovan notes, there was much to Truman's credit by 1952: the founding of NATO and containment of the Soviet Union, the induction of Japan and West Germany into friendly relations with the United States, the enshrinement of New Deal reforms and the passage of additional programs, the maintenance of atomic weapons in civilian hands.

Donovan's most explicit criticism centers on Truman's insufficient vision after the Second World War of how, "through a different policy toward the Soviet Union," the nuclear arms race could have been avoided, although the author concedes that this asks "a human being to solve what was in the circumstances a nearly superhuman problem."

Yet to reexamine these years is to note the degree to which Truman served as a canny and effective steward of foreign policy. He came to office with virtually no international experience. The structure that was in place to cope with the problems of the postwar period was but an embryo of the elaborate foreign policy government that serves modern presidents. The National Security Council, the Central Intelligence Agency, the Department of Defense, the policy planning staff at the State Department -- these new servants of presidential foreign policy-making did not exist for most of Truman's first term; they were only developing during the second.

With the aid of counselors and Cabinet officials such as Dean Acheson and George Marshall, Truman managed to persuade an American public weary of international involvement to assume an activist role in the world. With the aid of Republican leaders such as Arthur Vandenberg and John Foster Dulles, he managed, for the most part, to keep this commitment out of the blistering realm of domestic political antagonisms. Neither of these achievements was by any means a certainty in 1945.

Tumultuous Years is a worthy successor to Conflict and Crisis. Together, the two volumes should stand as the central source on the Truman presidency. The book is informed throughout by newly opened documents from the Truman presidential library and other archives that enable Donovan to reexamine these years with a depth and thoroughness not before possible. The author's meticulous attention to detail and his dispassionate approach are consistently in evidence. The effect is to provide us with a Harry Truman behind the caricature -- a president who, although woefully unprepared at the time of his accession, demonstrated surprising capacity for innovative leadership in guiding the nation through the perilous first eight years of the postwar era.