John F. Welch Jr. left General Electric Co. Sept. 7 after 41 years, half of them spent as chairman and chief executive. But his long shadow will linger.

Over two decades, the 65-year-old Mr. Welch remolded the enormous conglomerate in his own impatient, aggressive and alternately charming and overbearing image. He hand-picked and tutored the team that took over upon his departure. He pressured GE workers in plants and offices around the globe to drive themselves to meet ever-more-demanding efficiency standards, as writ in the gospel according to Welch.

And his influence doesn't end at GE. Welch progeny currently head more than a dozen U.S. companies. Hundreds more hold senior corporate posts. Workers who have never been near GE are familiar with Welch catch phrases like "fix, close or sell" and Welch-style employee ranking systems. In Japan, he is almost a folk hero. His forthcoming book and plan to stay active by advising CEOs will keep his name in the public realm.

Of course, the Welch era ended on a less than stunning note. His intended coup de grace, the proposed $45 billion acquisition of Honeywell International Inc., collapsed amid opposition from European regulators. Mr. Welch failed to persuade the officials that the deal wasn't anticompetitive, a rare defeat for an executive who prides himself on being a skilled negotiator.

GE took other hits in 2001, too. None galls Mr. Welch more than the decision of a White House administration he backed to force GE to pay hundreds of millions of dollars to dredge portions of the Hudson River in New York, where it dumped polychlorinated biphenyls, or PCBs, before they were banned in 1977. Mr. Welch fought such a step for his entire tenure.

Still, Mr. Welch says, the biggest surprise of being CEO for him was "how much fun it is. You get a chance to do everything, you get all these resources, you get great people, you get to try out a lot of ideas. You can go to bat, take swings, try things, see people you think are potential stars and move them quickly. Life is pretty damn good."

Why is Mr. Welch viewed as an icon? He wasn't, after all, an inventor like Henry Ford, or even an entrepreneur like Microsoft Corp.'s Bill Gates or Sam Walton, founder of Wal-Mart Stores Inc. It's sometimes forgotten that the company he took over on April 1, 1981, already had a 100-year history of management and technological innovation dating back to Thomas Edison.

Mr. Welch's immediate predecessor, a lean, deliberate Englishman named Reg Jones, had been among the nation's most-admired CEOs and twice was asked to join President Jimmy Carter's cabinet. Over the previous five years of inflation and recession, oil-price increases and a flat stock market, GE's earnings had grown nearly 63%, on sales growth of 59%.

But Mr. Welch brought a charisma and manic drive different from his predecessors. Where the ideal GE manager had been polite, slightly distant and focused on process, Mr. Welch, a chemical engineer who had never worked outside GE, had a reputation as a pushy hothead who rubbed some the wrong way but prodded his team to new heights. He insisted that a life-or-death global marketplace was about to ambush GE and the rest of American business, and that a complete overhaul of stodgy U.S. corporations was needed to meet it.

"Jack was an enemy of the bureaucracy," says Walter Wriston, the former Citicorp leader who sat on GE's board for 31 years until the late 1980s. "He had an IQ that's way off the chart and was extremely impatient with things that didn't move very rapidly. A lot of us thought that's exactly what the company needed."

As head of a large old-line company, Mr. Welch had a lab to test his ideas. As much as any business figure of his era, he was an architect of the reshaped industrial landscape of today and its business ethos of constant cost-cutting, global growth and an emphasis on shareholder returns.

With an intense focus on the bottom line, Mr. Welch spent his early years emphasizing a few simple but influential precepts, starting with his now-famous dictum that GE should be No. 1 or No. 2 in all businesses or get out of them. He dumped those with low-growth prospects, like GE's name-brand clocks, TVs and toaster ovens, while expanding financial-service provider GE Capital into a powerhouse and entering broadcasting with the $6.5 billion purchase in 1986 of RCA Corp., owner of the NBC TV network. He became a deal-making machine, overseeing 993 acquisitions with a total value of just over $130 billion, while selling 408 businesses for a total of about $10.6 billion.

Most famously, he shed more than 100,000 jobs during the 1980s -- a fourth of GE's work force -- through mass layoffs, divestitures and forced retirements. Tens of thousands of other high-paying manufacturing jobs were moved to cheaper, union-free locales overseas as GE embarked on a global expansion spree that is still going on. Under heavy fire from unions and many longtime GE veterans, Mr. Welch gained a reputation as a bully, which he sort of liked, and the nickname "Neutron Jack," which he has always hated but has never quite been able to shake.

His targets were GE's layers of middle managers. Storming about the company, Mr. Welch repeatedly scolded them to forget their lengthy memos and thick planning books, lecturing, "I don't want planning. I want plans." Those who didn't get with the program often got bounced.

Climbing the GE ladder, Mr. Welch "was a guerrilla fighter," says Bob Wright, a GE vice chairman, head of NBC and a close friend. "He was always personally vulnerable, never asked for any job security, never had a contract or employment agreement of any type." As CEO, he says, Mr. Welch "was either going to rescue the bureaucrats from their own fate or he was going to get rid of them because he couldn't figure out why they would be in that situation."

In all, GE's employment dropped from 402,000 at the end of 1980 to as low as 220,000 in the mid-1990s. It is back up to 314,000 today, mostly because of acquisitions.

At the top levels of business, many managers praised the Welch approach as liberating. "I still remember him coming to Louisville, and saying, 'Lemme tell you how I'm going to get rid of all this bureaucracy,' " says Bruce Albertson, formerly an executive at GE Appliances in Louisville, Ky. "Everyone was sitting there saying, 'Yeah, right.' But he ripped the bureaucracy right out of the middle of that company. All that churn we used to do, preparing internal charts for people who gave them to someone else who gave them to someone else who gave them to Jack, did go away."

Yet the upheaval, then unprecedented for a successful company, upended thousands of lives and severely strained the bonds between GE and its workers in Rust Belt towns like Schenectady, N.Y., and Lynn, Mass., where the company had deep roots. Both inside and outside GE, restructuring and layoffs became an accepted part of a manager's tool kit and a constant worry for workers.

"It became a lot more intense," recalls Richard Robinson, a former technical worker in the engineering department of a GE plant in Salem, Va., that makes industrial drives. His unit, admittedly a struggling performer, set aggressive goals every year, he says, "and we would meet and beat those goals, but it was never good enough. It was always, 'We could have done more.' We felt the philosophy at General Electric was that they could replace us in a heartbeat." Mr. Robinson was laid off in 1997, recalled a few months later, then cut for good in 1998 after 29 years with the company.

Mr. Welch's view is that he took the necessary steps to protect GE and thus the majority of its workers. Layoffs and anxiety "happen when businesses aren't strong enough. Winning models provide job security," he argues. "The idea that you can sit around and have this benevolent institution ... they don't survive. Look at the dot-coms."

Mr. Welch also oversaw his share of scandals, from the company's 1985 guilty plea to submitting time cards for too much overtime on government contracts to the 1994 bond-trading scandal at its former Kidder Peabody & Co. investment-banking unit.

But even critics concede Mr. Welch powerfully increased GE's financial might. The company's 2000 earnings of $12.7 billion were more than eight times the $1.5 billion profit it reported in 1980. Revenue has more than quintupled to $129.9 billion. As of just before Mr. Welch's departure, GE shares had risen about 5,096%, inclusive of dividends, since the day he  took over, according to Ned Davis Research Inc., or about 21.3% a year. The S&P 500 increased 1,433% over the same period, or about 14.3% a year, also inclusive of dividends.

Certainly Mr. Welch benefited from one of the biggest business booms ever seen, not to mention a soaring stock market that lifted most boats. (He also benefited personally, last year alone receiving compensation of more than $120 million.) But in addition, he steered GE through a tumultuous era of rapid business and technological change in which many other old-line companies, from once-mighty AT&T Corp. to perennial GE rival Westinghouse Corp., stumbled badly. In Mr. Welch's first year, GE was the nation's seventh-largest company, with a market capitalization of $13 billion. Today it is No. 1, its market capitalization at about $400 billion.

With his controversial methods and outspokenness, Mr. Welch also won prominence at a time when businessmen morphed into celebrities. Where GE executives formerly cultivated a cool, slightly distant manner, Mr. Welch, a former high-school hockey captain from a working-class family in Salem, Mass., is a combustible mix of restlessness, bluntness and emotional volatility.

With a warm public manner and lack of pretense, he usually insists that people call him "Jack," and manages to remember the first names of thousands of employees and shareholders. At 5-foot-8, shorter than many peers, and with a heavy New England accent and a stammer he has fought since childhood, he at times even seems vulnerable.

Kevin Sharer, a former GE executive who is now chairman and CEO of Amgen Inc., remembers being summoned with his immediate boss to Mr. Welch's office one Friday afternoon a few months after he started. "He poured us a cocktail and told me how happy he was that I was there, and that really was powerful," recalls Mr. Sharer.

He also possesses a macho, locker-room sense of competition, a love of argument and a sarcastic, teasing humor that at times cuts too deep. An admitted workaholic who loved putting in days of 12 hours or more and dragging home binders of stuff to read at night, he demanded the same commitment from others. When angry, he could lash out with lacerating, personal diatribes that sometimes left shamed managers hurt and speechless.

Coloring his encounters were a quick, keen intelligence and intensity that could seem both appealing and, at times, frightening. "Even when he has fun, he's driving himself," said Paolo Fresco, chairman of Italian automotive giant Fiat SpA and a former GE vice chairman, in an interview last year. "He won't give up till he has won, whatever he does."

In recent years, Mr. Welch focused much of his time on management systems and developing talent to make GE, as he put it, into a "learning organization." He was often suspicious of the "soft stuff" of management, including some of the programs with which he is now associated. He doubted the quality movement for a long time and accepted the Six Sigma efficiency plan, which GE now touts, only after executives imported it while he was recovering from bypass surgery in 1995. Similarly, Mr. Welch was long something of a technophobe, and embraced GE's recent effort to move functions to the Web only after years of pleas from some managers.

But once he made up his mind, he showed an undeniable talent for driving change throughout the company, thanks to his communication skills and a reorganization that had greatly increased the CEO's power. He sought to replace the fierce "Neutron Jack" image of the 1980s with that of the sweater-clad elder statesman of GE's Crotonville, N.Y., management-training center. He regularly preached "differentiation," his system of rewarding great managers and weeding out bad ones. To the end, Mr. Welch kept his hands tightly on financial targets and performance reviews, and made the final decisions on all options grants to workers and large acquisitions. He kept close tabs on his 600 top managers and frequently challenged them with information picked up through his own network of workers and customers.

It is as a manager that Mr. Welch would most like to be remembered. He would like to think his contribution to management was the notion "that every mind counts," he says. "You work like hell in an organization to be sure you put the mechanisms in to raise the intellectual level of the organization by taking everyone's ideas, constantly searching the world for the best ideas and making sure everyone knows their ideas count."

Did he do that? "You should measure my success eventually by how well GE does in the next five years," he says. "If I did my job right, they won't be saying it was a one-man show."