Bloomberg | A unit of Aon Corp., the world’s largest insurance broker, sued its closest rival, accusing Marsh & McLennan Cos. of seeking to steal trade secrets, poach clients and “rob Aon of its key employees.” Aon Risk Services Northeast Inc., whose parent is based in Chicago, filed a complaint today in Manhattan federal court against New York-based Marsh & McLennan and three ex-employees who recently left the firm.

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