DuPont CEO Ellen J. Kullman is hitting back at Trian Fund Management, the activist investor that wants to break up the company. Earlier this month, Trian lashed out at DuPont for what it sees as underperformance. The firm wants to install four of its nominees on DuPont’s board. Contrary to Trian’s claims, Kullman writes to shareholders, DuPont has been improving profitability and providing shareholder returns in excess of those of similar companies. DuPont and Trian representatives met 20 times to no avail, Kullman says. “Despite our engagement, they presented an ultimatum to DuPont that they have continued to reiterate to us—break up the company, put Trian on the DuPont Board, or face a proxy fight,” she writes. Trian’s signature suggestion for DuPont—breaking up the company further after the spin-off of its performance chemicals business—is “high risk and would destroy shareholder value,” Kullman maintains.