American International Group Inc.'s John Keogh, head of corporate board coverage, left to join Ace Ltd. after more than 20 years at the world's largest insurer.

Keogh, 41, was named chief executive officer of Ace Overseas General, the foreign property and casualty insurance unit of Bermuda-based Ace. He succeeds Gary Schmalzriedt, who will retire, Ace said in a statement yesterday.

"More than half of Ace's property and casualty business comes from outside the United States," Ace CEO Evan Greenberg said. "John brings substantial management and underwriting expertise."

At AIG, Keogh was CEO of National Union Fire Insurance Co., one of the biggest sellers of coverage protecting directors and officers against lawsuits. John Doyle, president of AIG's American Home Assurance Co., assumed his responsibilities.

Greenberg was once in line to succeed his father, Maurice (Hank) Greenberg, as CEO of New York-based AIG. The elder Greenberg was removed from AIG last year after state and federal regulators began investigating its accounting.

Schmalzriedt will remain chairman of Ace Overseas General until October 1, Ace said.