Stephen E. Ambrose, 66, a professor emeritus of history at the University of New Orleans who as a best-selling historian and biographer wrote more than 30 books that told stories of the American West and American statesmen and warriors to an admiring general public, died of lung cancer Oct. 13 at a hospital in Bay St. Louis, Miss.

Dr. Ambrose was the author of multiple-volume biographies of U.S. presidents Dwight D. Eisenhower and Richard M. Nixon.

He spent 20 years on his Eisenhower books and a decade on the Nixon volumes. Both biographies were praised by historians and critics as thoughtful, readable and authoritative accounts of presidential lives that included new insights.

Late in his career, Dr. Ambrose gained fame as the author of a series of bestsellers, many of them dealing with the U.S. military campaigns of World War II and featuring the fruit of numerous interviews he and his assistants had with the officers and especially the enlisted men who had gone overseas.

These included "D-Day June 6, 1944: The Climactic Battle of World War II," "Citizen Soldiers: The U.S. Army From the Normandy Beaches to the Bulge and the Surrender of Germany," "The Victors: Eisenhower and His Boys: The Men of World War II" and "The Good Fight: How World War II Was Won," all of which were published in the 1990s.

His 1992 book "Band of Brothers: E Company, 506th Regiment, 101st Airborne, From Normandy to Hitler's Eagle's Nest" was the basis for a cable TV miniseries that was brought to the screen by Tom Hanks and Steven Spielberg. Dr. Ambrose also was a consultant to "Saving Private Ryan," the World War II film starring Hanks and directed by Spielberg.

Dr. Ambrose, who made something of a career as a film consultant and sought-after lecturer, once joked on a late-night TV talk show that he doubted the value of some of his advice. He illustrated this with the advice he gave Spielberg on "Private Ryan," which was to get rid of Hanks, who the historian said was much too old to play a World War II Army infantry captain. Spielberg said he was sticking with Hanks.

Another of Dr. Ambrose's bestsellers was "The Wild Blue: The Men and Boys Who Flew the B-24s Over Germany." The 2001 book focused on the bomber commanded by the future South Dakota senator and Democratic Party presidential nominee George S. McGovern and on McGovern's crew. The history, again profiting from extensive interviews, was another book that brought home the horrors and suspense of war.

Dr. Ambrose, who had described himself as a hero worshiper, told one reporter that he came to this form of history from his work on Eisenhower and from childhood memories of returning World War II soldiers.

"I thought the returning veterans were giants who had saved the world from barbarism," he said. "I still think so."

But Dr. Ambrose wrote on topics other than politics and wars. His 1996 book "Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West" was a panoramic saga of the great and adventurous Lewis and Clark trek of exploration from St. Louis to the Pacific and back.

His 2000 bestseller "Nothing Like It in the World: The Men Who Built the Transcontinental Railroad 1863-1869" told not only of the planning and financing of the quest but also of the influence of railroads on the American West and the national economy. And it gave voice to the men who did the labor for the Central Pacific and Union Pacific railroads.

Mr. Ambrose, who was born in Decatur, Ill., grew up in Whitewater, Wis., where he was captain of his high school football team. He was a 1957 history graduate of the University of Wisconsin and received a master's degree in history from Louisiana State University and a history doctorate from Wisconsin.

He taught at what is now the University of New Orleans from 1960 to 1964, and again from 1971 until retiring in 1995. He served on the faculty of Johns Hopkins University from 1964 to 1969, the Naval War College in 1969 and 1970, and Kansas State University in 1970 and 1971.

As with many academic historians, his first book was based on his graduate work. It focused on Henry Halleck, the Civil War general who served as President Abraham Lincoln's chief of staff and was widely regarded as one of the most brilliant men to wear this country's uniform. Published in 1962, "Halleck: Lincoln's Chief of Staff" was a sound overview of a brilliant staff officer but was not a bestseller.

But one old soldier who had been something of a staff officer himself and who was farming in retirement in Pennsylvania loved the book. He was so taken with it that he called Dr. Ambrose and invited him to his farm. The caller was Eisenhower, a five-star Army general and former president.

Dr. Ambrose, who later recalled he was flabbergasted by the call, traveled to Gettysburg, where he hit it off with Eisenhower and began a series of books dealing with Eisenhower and World War II.

If Dr. Ambrose gained fame and the admiration of the reading public, he was not universally acclaimed by other American academic historians. Some wrote that if his books were readable and accurate, they had little in the way of grand conclusions or historical theory.

Some feel that jealousy helped lead to the bump in Dr. Ambrose's writing career this year when accusations of plagiarism were raised against him. It turned out that while questioned passages in a couple of books lacked quotation marks, the quotes were footnoted. Dr. Ambrose apologized for sloppy editing but denied that he had committed plagiarism.

Douglas Brinkley, also a best-selling historian and a former student of Dr. Ambrose's, remembered him as "the great populist historian of America. He didn't write for intellectuals, he wrote for everyday people."

Pulitzer Prize-winning historian and Kennedy White House aide Arthur Schlesinger Jr. said Dr. Ambrose "combined high standards of scholarship with the capacity to make history come alive for a lay audience."

Dr. Ambrose's autobiography, "To America: Personal Reflections of an Historian," is scheduled for publication in November. "I want to tell all the things that are right about America," he told the Associated Press in a recent interview.

It also will tell the story of how a left-wing intellectual and antiwar demonstrator who hated Nixon became a thoughtful biographer of that president and a historian who saw the glory in the actions of U.S. warriors.

Dr. Ambrose, whose cancer was diagnosed this year, told the New Orleans Times-Picayune that he was inspired to continue writing by the example of Ulysses S. Grant. That old general grimly finished his autobiography, widely considered the best presidential memoir ever written, while painfully dying of throat cancer.

Stephen E. Ambrose's subjects included World War II and the Lewis and Clark expedition.