Forrest E. Mars Jr., who helped build his family’s candymaking empire into one of the richest businesses in the world, stocking treat jars around the globe with Milky Ways, Snickers and M&Ms while maintaining the company’s tradition of extreme secrecy, died July 26 at a hospital in Seattle. He was 84.

The cause was complications from a heart attack. His death was announced by Mars Inc., the McLean, Virginia-based company where Mars and his brother, John, took over from their father, Forrest E. Mars Sr., as co-presidents in 1973. Forrest Jr. retired in 1999.

Mars’s grandfather, a small-time confectioner named Frank Mars, founded Mars in 1922. The company exploded over the next two generations into a global powerhouse of candy bars, pantry items and pet foods.

The company credited Forrest Jr., John and their sister, Jacqueline, with increasing sales from $1 billion to $35 billion and with employing 80,000 people in 78 countries. According to Forbes magazine, the Mars family, with an estimated worth of $78 billion, is the third-richest in the United States, behind only the Waltons of Wal-Mart and the Kochs of Koch Industries.

Besides the Milky Way – marketed outside the United States as the Mars bar – Mars’ sweets brands include 3 Musketeers, Twix, Starbust, Skittles and Dove ice-cream bars. Since its purchase in 2008 of the Wm. Wrigley Jr. gum company for $23 billion, Mars also has produced Wrigley’s Doublemint gum, Life Savers and Altoids mints.

In the breakfast and main-meal categories, Mars products include Flavia coffee and Uncle Ben’s rice. Among its pet offerings are the Pedigree, Iams, Whiskas, Royal Canin and Eukanuba brands of pet food.

In his taste for privacy, Mars followed in the tradition of his father, who was credited with creating M&M’s, the candy-coated treats billed to “melt in your mouth, not in your hand.” As executives, father and sons were as elusive as their products were ubiquitous.

The company’s secrecy has drawn frequent comparisons to its neighbor in the nearby community of Langley, Virginia – the CIA. But over the years, a portrait emerged of a business operation at Mars that was equal parts effective and eccentric, created by Forrest Sr. and maintained by Forrest Jr. and his brother over decades of change in technology and international commerce.

In one oft-told episode, Forrest Mars Sr. introduced himself to other Mars executives as a “religious man,” then fell to his knees and recited, “I pray for Milky Way. I pray for Snickers.” Like their father, Forrest Jr. and John Mars displayed single-minded devotion to their business. They were widely reported to have paid their employees above-average wages but also to have demanded above-average loyalty.

“I was truly astonished by [Mars’s] dedication to keeping his father’s values in place and doing it while advancing the company into the modern age,” Joël Glenn Brenner, a former Washington Post reporter and the author of the book “The Emperors of Chocolate: Inside the Secret World of Hershey and Mars,” said in an interview. “Nothing has changed at that company from the beginning.”

Among the Mars family values was an intense, almost manic focus on quality. Millions of M&M’s are discarded when the M stamped on each piece of candy is found to be off-center. If a minuscule hole is spotted in a single Snickers bar, the entire run may be tossed, Brenner reported in The Post. It was said that employees in the pet-food division performed quality control by tasting their products.

All employees, co-presidents included, clocked in and out, and 10 percent bonuses were awarded to those who reported on time for duty. To remind workers of their responsibilities – and the consequences of not meeting them – the Mars brothers displayed a butcher’s block in the McLean headquarters proclaiming, “Head on the block responsibility.”

There were no offices, and all employees did their own grunt work, including making photocopies. They were warned never to speak to reporters and to rigorously defend the company’s privacy. When factory machines required repairs, contractors were reportedly brought into the facilities blindfolded.

Forrest Jr. and John Mars inherited a company that was already multinational, but Brenner credited them with expanding its reach even further, including into Russia after the Cold War and into China, the Middle East, Africa and Latin America.

The brothers also led the company through an arch rivalry with the Hershey Co., maker of Kisses, York Peppermint Patties and peanut-butter Reese’s Pieces. One misstep occurred in 1982, when Steven Spielberg released the film “E.T. the Extra-Terrestrial.” Mars Inc. declined a chance for product placement, a decision that allowed Reese’s Pieces – rather than M&M’s – to be the alien’s favorite treat. Washingtonian reported that the film, which became a classic, spurred sales of Reese’s Pieces.

A sad irony of the Mars family success was the fact, widely reported, that it was the product of an unhappy home. Forrest Sr. was described as a harsh, often demeaning father who would criticize his children during mealtime.

“The Mars children have a terrible time with food,” a family acquaintance told Brenner. “They are all yo-yo dieters, they never sit down for a meal. They have awful recollections surrounding food and their father.”

Forrest Edward Mars Jr. was born in Oak Park, Illinois, on Aug. 16, 1931 .When he was a child, his father moved the family to Slough, England, where Mars Sr. branched off from his own father’s candy business.

Forrest Sr. was so parsimonious with his family that his wife and children eventually returned to the United States, where Mr. Mars graduated in 1949 from the private Hotchkiss School in Connecticut. He went on to receive a bachelor’s degree in economics from Yale University in 1953 and an MBA from New York University in 1958.

The next year, he joined his father’s company as financial staff officer for M&M’s. Shortly thereafter, the company posted him to the Netherlands, where he oversaw the construction of a factory, and later to the Paris region, where he was director of Mars France.

In 1970, he moved to the McLean headquarters, where he became a vice president and eventually co-president. Forrest Sr. died in 1999 at 95.

The extent of the Mars family’s philanthropy, great or small in the scheme of its wealth, was not widely known, in keeping with its desire for privacy.

Mars supported environmental initiatives such as the American Prairie Reserve in Montana as well as historical projects, including the Colonial Williamsburg Foundation and the Mars Hall of American Business at the Smithsonian Institution’s National Museum of American History.

He lived in the Rosslyn community of Northern Virginia before moving to Sheridan, Wyoming, in 1999. The company announcement of his death described him as an “explorer, who loved adventuring in his expedition ship in some of the wildest places in the globe, including navigating the North West passage.”

His marriages to the former Virginia Cretella and the former Deborah Adair Clarke ended in divorce. Survivors include his wife of several years, the former Jacomien Ford; four daughters from his first marriage, Victoria Mars, Valerie Mars, Pamela Mars-Wright and Marijke Mars; his sister and brother; 11 grandchildren; and two great-grandchildren.

Mars rarely if ever granted interviews or spoke to the public. But once, appearing before students, he offered at least in part an explanation of why he had conducted his business and his life in the curious, at times confounding, way that he had.

“Privacy at times today seems a relic of the non-media past,” Brenner quoted him as saying, “but it is a legal right – morally and ethically proper and even desirable – and a key to healthy, normal living.”