Ellen Kullman is retiring as chairman and CEO of chemical giant DuPont (DD) after six years at the helm.
Kullman, who ranked fifth on Fortune’s 2015 list of Most Powerful Women in Business, will be replaced in the interim by Edward Breen, a member of the DuPont board of directors. The changeover will be effective next Friday, October 16.
The move comes as a surprise, as the 59-year-old Kullman has been somewhat of a hero among CEOs after DuPont’s shareholders voted down activist investor Nelson Peltz’ proxy fight to split up the company. The vote occurred this past May after nearly two years of back-and-forth arguments between Kullman and Peltz’s Trian Group.
Aside from winning the lengthy battle with Peltz, Kullman been praised for strategic moves to streamline the conglomerate, such as the spinoff of DuPont’s coatings division in 2013, as well as that of its Chemours subsidiary in July of this year. Peltz, however, said these moves were not enough to fix its “underperformance.”
The fight with Peltz was emblematic of Kullman’s tumultuous tenure as CEO. When she was appointed president in October 2008, “the world fell apart,” she told Fortune’s Carol Loomis in an interview in 2010. Soon after moving up to CEO in early 2009, she oversaw two restructurings and laid off thousands of employees.
The retiring CEO is DuPont “through and through,” wrote Fortune’s Stephen Gandel in a piece about the war with Trian earlier this year. She grew up near the chemical giant’s headquarters in Delaware and has been with the company for 27 years.
Still, the company has struggled financially under Kullman’s leadership. Last year, revenue declined to $36 billion, while profits sank 25% to $3.6 billion. Shares of the company are down 27% this year.
According to the company’s statement, DuPont has revised its operating earnings projections downward from $3.10 to $2.75, citing a strengthening U.S. dollar. The company also said it plans to cut $1.3 billion in costs by the end of 2016 and about $1.6 billion by the end of 2017, though it didn’t specify how.
For an in-depth look at DuPont’s war with Nelson Peltz, read Fortune’s coverage here.
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