Apple’s newly appointed chief operating officer has been a major force behind some of the company’s biggest initiatives.

Jeff Williams has for years overseen Apple’s sprawling, complex global supply chain, assuming that role after Tim Cook was named the company’s chief executive. His responsibilities have expanded over time to include work on key products, such as the development of the Apple Watch, the company’s first new product category in five years.

“Jeff is hands-down the best operations executive I’ve ever worked with,” Cook said in a statement.

The lanky executive with a calm demeanor, who joined Apple in 1998, has received little of the media attention lavished on other Apple executives — though lately, he has grown more prominent, appearing onstage at an Apple event last March, where he talked about Apple’s ResearchKit medical research initiative, as well as an onstage interview at the 2015Code conference.

A person familiar with the matter cautioned against concluding that Williams will be Cook’s eventual successor, noting that the company employs several world-class executives capable of running a company (indeed, retail chief Angela Ahrendtsleft Burberry, where she was CEO, to join Apple in 2014).

Wall Street applauded Williams’s elevation to chief operating officer, a position that has been vacant since 2011.

“Williams is extremely well respected within Cupertino and knows Apple’s inner workings as well as anyone out there,” said Daniel Ives of FBR Capital Markets. “Cook needs a right-hand man, and Williams is a nice addition to the management team.”

In that rare and wide-ranging interview at Code, Williams talked about the sheer breadth of Apple’s manufacturing supply chain with Re/code co-founder Walt Mossberg. He discussed the responsibilities of overseeing the 3,000 engineers who “figure out how we do the things we do,” to the logistics of shipping and distributing millions of products, to the 45,000 people who answer the phones when customers have questions.

The executive also shepherded development of the Apple Watch long before terms like “wearables” or “smartwatches” were bandied about.

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