Sears, Roebuck & Co. said yesterday that its chairman and chief executive, Edward Brennan, will retire Aug. 9 and be succeeded by Arthur C. Martinez, who now is chairman of the Sears Merchandise Group and credited for much of the company's dramatic retailing turnaround. He joined Sears in 1992 from Saks Fifth Avenue. Sears Vice Chairman James Denny will also be stepping down on Aug. 9.


