Financier Carl Icahn on Thursday launched a proxy battle to force Yahoo to reopen buyout talks with Microsoft, saying the Yahoo board had acted "irrationally" in refusing its $47.5 billion offer. Icahn harshly criticized Yahoo for the breakdown in talks, and said he had accumulated 59 million shares and options in Yahoo and assembled a 10-member dissident board slate for election at Yahoo's annual meeting on July 3.

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