March 27, 2015 2 min read

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When Tim Cook assumed the role of Apple’s CEO in 2011, he had some near-impossible shoes to fill. Steve Jobs was already a legend, his status as a genius, once-in-a-century innovator having been cemented long before his death six weeks later.

How do you directly follow the force behind the iPhone, iMac, iPad and iTunes? Simply put, there is no way to prepare, Cook told Fortune in an in-depth interview. After becoming CEO, he was immediately beset by predictions that Apple would sink without Jobs and that, as the company's new leader, he would usher in an age of un- . This, of course, has so far failed to play out: Under Cook, the company has rolled out the Apple Watch and Apple Pay, among other potentially game-changing projects.

Cook says his baptism-by-fire – which included the Apple Maps debacle and some high-profile hires and subsequent firings – taught him valuable lessons about the art of leadership.

Related: Tim Cook Reveals the Sectors Apple Wants to Conquer Next

Cook has an operations background. As an engineer, he told Fortune, you have the luxury of analyzing specific problems. But as CEO, there are so many realms -- , culture, marketing, product design etc. – that need to be managed at once. “You’re engaged in so many things that each particular thing gets a little less attention,” he said. “You need to be able to operate on shorter cycles, less data points, less knowledge, less facts.”

As CEO, he says, “if you believe that the most important data points are people, then you have to make conclusions in relatively short order.” It’s a lesson Cook learned in early 2013, when he hired John Browett, the former head of the U.K.-based discount electronics chain Dixon’s. It was quickly apparent that Browett didn’t fit in with Apple’s culture, and instead of hemming Cook swiftly cut him loose, firing him in March of that year. “You want to push the people who are doing great,” told the outlet. “And you want to either develop the people who are not or, in a worst case, they need to be somewhere else.”

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