Mr. Sullivan, 50, replaced the 79-year-old Greenberg as CEO on March 14, as pressure from regulatory probes forced AIG's board to sideline its longtime leader.

The new CEO himself admitted that he faces a “daunting task” filling the void left by Mr. Greenbergwho had been running AIG since 1967 with a very high profile, and in the process turned a small carrier into the world's biggest insurer with $100 billion in revenue.

But while it will take time to adjust to the idea of AIG without Mr. Greenberg at the helmthe AIG Web site, for example, still identified Mr. Greenberg as its CEO on the corporate governance section more than a week after the shuffleMr. Sullivan was generally given a top rating by his colleagues and industry observers alike.

“Hes very well regarded in the industry, a long-term AIG employee who progressively got more responsibility over the 30-plus years he's been there. Now he's gotten all the way to the top, so he's a very capable individual,” said Dinos Iordanou, CEO of Arch Capital Group Ltd., who worked at AIG from 1977 to 1987 as senior vice president of the American Home unit.

Mr. Iordanou also told National Underwriter that while Mr. Sullivan has a keen sense of humor and is very well liked within AIG, “don't be mistakenhe's also a tough manager. He has toughness in him that comes in a different way. At the end of the day, I think he will do extremely well. He's clearly worthy of the appointment he got.”

One current AIG executive who declined to be identified said that many employees are encouraged by the prospect of having Mr. Sullivan as the companys next CEO. “He is very highly thought of within the company and is a very well-respected guy here,” the executive said.

Paul Newsome, an analyst at investment firm AG Edwards & Sons Inc., who has met and talked with Mr. Sullivan, described the new CEO as an “impressive guy.”

“Hes been with AIG for a long timehe embodies the AIG culture,” Mr. Newsome said. “He's almost certainly going to be a gentler, kinder CEO. The perception is that he's a little more laid back, a little bit easier going, less rough around the edges than Mr. Greenberg.”

Yet despite differences in personal styles between Mr. Sullivan and Mr. Greenberg, Mr. Sullivan is also known for his directnessand he also, like Mr. Greenberg, has a reputation as a hands-on micro-manager.

“My guess is that you will see a very similar management style from Mr. Sullivannot too much change from Mr. Greenberg, but probably more cooperation among senior managers than you would have seen previously,” Mr. Newsome predicted.

One reason Mr. Sullivan may need to cooperate extensively with other senior managers is his lack of experience on the life-insurance side.

“Yes, this is a concern. Chief Operating Officer Donald Kanak is perceived to have a much stronger life-insurance background,” Mr. Newsome noted, referring to another top AIG executive who was widely seen as Mr. Sullivans main competitor for Mr. Greenbergs job.

Mr. Kanak, 52, who had been serving as AIG's co-chief operating officer along with Mr. Sullivan for the past two years, has been named executive vice chairman and the sole chief operating officer during this months management change. Mr. Newsome forecast that keeping Mr. Kanak and the rest of the senior management team working together will be an “important part of Mr. Sullivan's success.” He added that “Mr. Sullivan's tenure as the CEO will be more of a team effort.”

Mr. Sullivan, born in Dagenham near London, is now one of the most powerful foreign-born executives running a U.S. corporation, completing a rise to the top that began 34 years ago.

Mr. Sullivan first started working in the insurance industry at the age of 16 when he left school to work for Sun Alliance. He joined AIG at 17 at the company's U.K. non-life insurance business in 1971, progressively rising up the ranks to become AIGs property insurance manager for the U.K. region.

In 1988, he was named manager of AIG's overseas unit's office in London, and in 1993 became managing director of AIG Europe Ltd. In 1996, he relocated to New York to become chief operating officer of AIG's overseas insurance operations.

Mr. Sullivanan executive little known to investors and the public for most of his careerwas thrust into the media spotlight in 2002 when, in a management shuffle, he was positioned as one of a few potential successors to Mr. Greenberg. In an unexpected move, Mr. Sullivan was named vice chairman and, along with Mr. Kanak, co-chief operating officer of AIG and was elected to the board.

This month, when he was named AIGs new chief executive, Mr. Sullivan told analysts: “It is a daunting task to step into the shoes of Hank Greenberg. Thanks to his leadership, AIG's business units are managed by tested professionals who are leaders in their fields. We have an extremely strong business and our financial fundamentals remain intact.”

AIG, Mr. Sullivan also noted, is committed to cooperating with various government authorities in their ongoing investigations of his firm. “We take these matters seriously and want to bring them to resolution,” he said.

Reproduced from National Underwriter Edition, March 25, 2005. Copyright 2005 by The National Underwriter Company in the serial publication. All rights reserved.Copyright in this article as an independent work may be held by the author.