Robert D. Stuart Jr., the politically active heir to the Quaker Oats Co. who led the company for 15 years and, as a student at Yale Law School in 1940, ignited the America First movement against U.S. intervention in what became World War II, has died. He was 98.

He died of heart failure on May 8 while traveling from France to the United States with his wife, Lillan, his son, Alexander D. Stuart, said Monday in an email.

Quaker Oats, maker of brands including Gatorade, Rice-A-Roni, Cap'n Crunch and Aunt Jemima, was bought by PepsiCo Inc. in 2001, which was the 100th anniversary of its founding in Chicago. Its roots go back further to the 19th century, when several businesses merged to become American Cereal Co.

One of those businesses, based in Cedar Rapids, Iowa, was run by Stuart's great-grandfather, John, and grandfather, Robert. His father, known as R. Douglas Stuart, served as Quaker Oats president.

As chief executive from 1966 to 1981, Stuart oversaw the introduction of instant oatmeal and Quaker Chewy Granola bars. He also continued the Chicago-based company's growth beyond its oatmeal roots. The 1969 purchase of Fisher-Price Toy Co. of East Aurora, New York, was Quaker Oats' first nonfood acquisition since 1942, when it had expanded into dog food by buying Chappel Brothers Inc., maker of Ken-L-Ration.

Quaker Oats turned Fisher-Price into an industry leader through national television advertising. Explaining the acquisition of the toymaker, Stuart said, according to a New York Times account, "The back of the cereal box on the breakfast table just seemed to be a logical fit between the cereal and toy businesses."

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Fisher-Price sales rose to $300 million in 1980 from $25 million in 1966, according to the Times. By 1990, though, the toy unit was being blamed for earnings declines, and Quaker Oats spun it off in 1991. It's been a unit of Mattel Inc. since 1993.

Stuart retired as CEO in 1981 when he turned 65, succeeded by William D. Smithburg, and remained chairman until November 1983.

"Two themes animated his leadership: a belief in the power of strong brands and the certainty that corporations like Quaker had a duty both to their shareholders and to the communities in which they lived and operated," Alexander Stuart wrote of his father.

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President Ronald Reagan appointed Stuart U.S. ambassador to Norway, a post he held from 1984 to 1989. Politically active throughout his life, he was a Republican Party committeeman from Illinois from 1964 to 1972 and served on the national Defense Base Closure and Realignment Commission in 1991 and 1993.

His first leap into politics made history.

At 24, he became founding national director of the America First Committee, the anti-war movement begun in 1940 at Yale University in New Haven, Connecticut, where he was attending law school.

Other Yale students involved in its formation included Gerald Ford, the future president; Robert Sargent Shriver Jr., who would become founding director of the Peace Corps; and Potter Stewart, a future Supreme Court justice.

In its first report on the movement, in November 1940, The New York Times quoted Stuart as saying that the push for U.S. intervention against German aggression "seems to come from those who want to go and save England. We are taking a stand for unity in defense and peace."

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Though the America First campaign went down in history associated with the anti-Semitism of famed aviator Charles Lindbergh -- "The three most important groups who have been pressing this country toward war are the British, the Jewish and the Roosevelt administration," he said in a September 1941 speech -- Stuart said its founding core consisted of Democrats and Republicans, Jews and non-Jews alike, who shared reasoned viewpoints against war.

"Most of us in our generation who were in any way thoughtful about history and international affairs learned that the U.S. didn't accomplish very much in committing troops to the First World War, which was a terrible slaughter of the talent of the Western world -- an internecine conflagration," Stuart said in a 2000 interview with Bill Kaufmann, editor of "A Story of America First," a book by Ruth Sarles published in 2002.

The Japanese attack on Pearl Harbor on Dec. 7, 1941, followed days later by Germany's declaration of war against the United States, spelled a sudden end to America First. Stuart, who had taken a leave from Yale to run the committee, enlisted in the U.S. Army and fought in Europe.

Lillan Lovenskiold; a sister, Margaret; another son, James Stuart; a daughter, Marian S. Pillsbury; eight grandchildren and six great-grandchildren.