Jack Trout advanced simple but widely influential marketing ideas in books that sold millions of copies. (Craig Cutler)

Jack Trout, whose concept of “positioning” has become one of the central tenets of marketing and whose ideas have been used in countless corporate campaigns and by the federal government, died June 4 at his home in Old Greenwich, Conn. He was 82.

The cause was intestinal cancer, said a daughter, Joanne Trout.

Mr. Trout and his longtime business partner, Al Ries, advanced simple but widely influential marketing ideas in books that sold millions of copies around the globe. Over the years, Mr. Trout helped devise marketing strategies for such companies as Apple, AT&T, IBM, Procter & Gamble and Southwest Airlines as well as the State Department and the Democratic Party.

In 1969, Mr. Trout coined the term “positioning,” which he and Ries further explained in articles in the publication Advertising Age and a 1981 book, “Positioning: The Battle for Your Mind.”

“Their thesis was that marketers needed to fill a hole in the consumer’s mind with the distinct attributes of their product,” Rance Crain, editor in chief of Advertising Age and president of Crain Communications, said in an email. “Up until that time products were all over the place in what they stood for, but Jack and Al emphasized that a brand needed to be consistent in the position it staked out in the consumer’s mind.”

Under the principle of positioning, companies develop a lasting identity by being connected to a simple idea or story. For years, the brand names Kodak, Coca-Cola, Goodyear and Xerox were practically synonymous with the products they made.

The problem, Mr. Trout said, is that too many companies dilute their brand names by branching out and ignoring their core strengths. In short, positioning is built on psychology and trust as much as commerce.

“Brand names tend to be one thing in the mind,” Mr. Trout told the Indian publication Business Today in 1997. “We have discovered that over a long period of time, you can only be one thing in the mind. If you try to become two things, or three, or four, you tend to become nothing in the mind.”

He and Ries developed another memorable business term by suggesting that companies could gain a competitive edge through “marketing warfare” — the title of a book they wrote together in 1983. (As part of the marketing campaign for the book, the authors donned Army helmets and rode down New York’s Fifth Avenue in an armored military vehicle.)

They argued that executives could exploit marketing niches by studying their competitors’ strengths and weaknesses, as if preparing for battle.

In the rental car business, Avis, the longtime also-ran to Hertz, devised the effective slogan “We try harder.” The 7UP soft-drink line couldn’t dislodge Pepsi or Coca-Cola, so it differentiated itself in memorable commercials by advertising itself as “the Uncola.”

“If you look at the war analogy, it is your soldiers versus their soldiers fighting over a territory,” Mr. Trout said in 1997. “And marketing warfare is between you and your competitor, fighting over customers.”

From time to time, the military itself was linked to marketing efforts. In the early 1990s, dozens of companies sought to align themselves with U.S. forces during the Persian Gulf War.

“You don’t want to be seen as supporting an unpopular war,” Mr. Trout told the Los Angeles Times in 1990. “This conflict is terrific: Everyone is looking good in their fatigues, drinking Gatorade, just kind of milling around. But if the shooting starts, it might be a different story.”

A decade later, after the 9/11 attacks, Mr. Trout was hired by the State Department to develop “Brand America” as part of an effort to improve international perceptions of the United States. After the invasion of Iraq in 2003, however, it became all but impossible to soften the U.S. image overseas.

“America had one idea attached to its brand,” Mr. Trout told the Christian Science Monitor in 2004. “We presented ourselves as the world’s last superpower. And that was the world’s worst branding idea.”

John Francis Trout, whose father was a salesman, was born Jan. 31, 1935, in New York City. He was a graduate of Iona College in New Rochelle, N.Y., where he played basketball and tennis. He served as a Navy aviator.

He worked for General Electric and the Uniroyal tire company before becoming president of Trout & Ries in 1969. He and Ries published other books, including “Bottom-Up Marketing” (1986) and “The 22 Immutable Laws of Marketing” (1992), before dissolving their company in 1994.

One of the businesses they promoted in the 1980s was President Trump’s now-closed casino Trump Plaza, which they dubbed “Atlantic City’s centerpiece.”

Decades later, Mr. Trout helped develop strategies for the Democratic Party.

“Jack Trout’s incisive understanding of communicating with the middle class provided a valuable pillar for our successful efforts to win the majority in 2006,” House Democratic leader Nancy Pelosi (Calif.) said in a statement.

Mr. Trout’s survivors include his wife of 60 years, the former Patricia Daley of Old Greenwich; six children, Timothy Trout and Susan Trout, both of New York, Joanne Trout of Riverside, Conn., Nancy Trout of West Hartford, Conn., Christine Acton of Annapolis and Peter Trout of Larchmont, N.Y.; two sisters; three brothers; and 15 grandchildren.

In later years, Mr. Trout continued to publish new books, including “Trout on Strategy” (2004) and “Repositioning” (2009), and maintained his belief that marketing was largely a matter of mind over numbers.

“Good marketing is good storytelling,” he said in 2009. “When you lose your line to the past, you don’t have a good line to the future.”