ROBERT A. LOVETT, who died this week at the age of 90, belonged to that remarkable generation of public men who set American policy for the postwar world. They built well. You will often hear it said that people never learn from history, but a great many Americans grasped the dire lessons of the failed peace after World War I. The United States, the only country with the strength to lead a stable international system, chose instead to withdraw from any very active role. The chaos and distress in Europe rapidly generated a second war and, when it ended, Americans were sharply divided over what was to happen next. Some wanted to return once more to splendid isolation. Others, among whom Mr. Lovett was prominent, remembered what had happened the last time, and very fortunately for the United States and for the world, they won the argument.

Through the late 1940s, as the nature of the Soviet challenge unfolded, the United States by degrees committed itself to the concept of economic aid and long-term military alliances to provide a firm foundation for liberal parliamentary democracy in Western Europe and Japan. Every part of that commitment, and particularly the aid, was fought out with great vehemence here in Washington. But that strategy has been successful beyond the hopes and calculations of even those people who believed in it most deeply.

Mr. Lovett, who had been an assistant secretary of war during the fighting, returned here in 1947 to work with Gen. George C. Marshall, then secretary of state, in persuading Congress to provide aid for Europe -- the Marshall Plan. When Gen. Marshall became secretary of defense in 1950, he again persuaded Mr. Lovett to become his deputy, and on the general's retirement, Mr. Lovett succeeded him as secretary through the end of the Korean War. He was a man with a high sense of public service who moved with assurance between his two careers, in government here and in investment banking in New York. There is much by which to remember him and the people with whom he worked in those crucial years, but the greatest of their memorials is the long and durable peace among the countries that fought in the two world wars.