n Patrick Buchanan's view of US history, 1897 was a very good year, with the nation protected by two vast oceans and President William McKinley promising to keep us out of war. A century of conflict has intervened, and Buchanan's views on foreign policy, shaped by a bitter isolationism, make him unfit to be president.

Yet George W. Bush wants to keep Buchanan in the Republican Party, and if he bolts, the Reform Party is considering nominating him for president. Based on the views expounded in his new book ''A Republic, Not an Empire,'' Buchanan has no place in the leading ranks of any party that aspires to the presidency.

In the book, Buchanan belittles McKinley for getting the United States into war with Spain and Woodrow Wilson for leading the nation into World War I. Buchanan reserves his harshest criticism for Franklin D. Roosevelt, ''anxious, even desperate'' to get the United States into World War II. In Buchanan's view, the United States should have done its utmost to avoid war with Germany or Japan, and Britain and France should not have resisted Hitler's aggression against Poland.

''Had Britain and France not given the guarantee to Poland,'' Buchanan writes, ''Hitler would almost surely have delivered his first great blow to Stalin's Russia. Britain and France would have had additional years to help build up their air forces and armies and to purchase, as neutrals, whatever munitions they needed from the United States. If the revealed horrors of Nazism in the East mandated a war, the Allies could have chosen the time and the place to strike.''

Buchanan's disdain of past conflicts shapes his perspective on the US role today. He opposes every Cold War alliance with the possible exception of NATO. He wants the United States to dismantle the accords with Japan and South Korea that have kept the peace in the North Pacific for four decades. He wants an end to the US military involvement in the Persian Gulf that has safeguarded the world's major source of oil. ''We are but 4 percent of the world's population,'' he writes, ''and cannot be held eternally responsible for the peace and security of half the planet.''

Much the same was said in 1919 just after World War I. Wilson was trying to fashion a new international order and agreed with the British on a treaty to protect France from German attack. That accord got lost in the debacle following the Senate defeat of the Versailles peace agreement with Germany - a rejection Buchanan supports.

If the United States had remained engaged in European security issues, Franklin Roosevelt could have helped prevent Hitler's occupation of the Rhineland on the border with France in 1936. Instead, Germany was allowed to pick off that territory, then Austria and Czechoslovakia, before Britain and France drew the line at Poland. The United States did nothing.

Once the war had begun with an unprovoked German attack on Poland, it was clear to Britain and France that Hitler could never be trusted. After France fell, Britain had to fight on, as Winston Churchill said, to prevent the world from sinking ''into the abyss of a new Dark Age made more sinister, and perhaps more protracted, by the lights of perverted science.''

Churchill understood, as Buchanan does not, that the victor in a Russo-German war would have dominated Europe from the English Channel to the Ural Mountains. If it were a draw, Germany would have controlled the industrial heart of the continent, and its engineers would have been working on missiles and jet fighters, both of which came into service by 1945 anyway. Could an atomic bomb have been far behind?

Franklin Roosevelt shared Churchill's insight. Had the United States not acted in concert with Britain and the Soviet Union, it might have faced a different kind of Cold War - against Nazi Germany and Japan. (Buchanan would have made a deal with the Japanese to avert Pearl Harbor.)

Roosevelt's policies inaugurated an era of US engagement with the world that continues to this day. While this approach has not been without peril, as shown in Vietnam, it has averted a world conflagration that would have been far worse than World War II, in which 55 million people died, among them 407,000 Americans. And today democracy, not Nazism, is the worldwide political ideal.

In Buchanan's view, those US casualties were unnecessary. He has earned Senator John McCain's rebuke for seeming to slight their sacrifice. Isolationists who shared Buchanan's worldview kept the United States from the steadfast commitment to European security that might have prevented World War II and that, when belatedly maintained with NATO, kept the peace during the Cold War.

Buchanan's isolationism should not have blinkered US policy in the first part of the 20th century. It has no place as the nation enters the 21st.