Microsoft said Chief Research and Strategy Officer Craig Mundie, 63, plans to retire in 2014 after two decades at the software company and has shifted to a new role as a senior adviser to CEO Steve Ballmer.

Eric Rudder, chief technical strategy officer, is taking over some of Mundie’s duties overseeing research, privacy and security, as well as technology policy, Ballmer said in an email to staff Dec. 14 that Microsoft made public Monday.

Mundie’s job switch marks the second change to the senior leadership team within the past two months. On Nov. 12, the company announced that Windows chief Steven Sinofsky was leaving.

After releasing the latest version of its flagship operating system in October, Ballmer is putting in place a new team to start planning the next upgrade to help Microsoft compete in a market that has shifted to mobile devices and computing over the Internet.

The team led by Rudder “continues to help shape the long-term technology-policy landscape in ways that will give our future products a clear path in the marketplace,” Ballmer wrote in the memo.

During his time at Microsoft, Mundie was responsible for Microsoft’s early efforts in software for handheld organizers, cars and televisions. He also developed technology policy in areas such as privacy and security, and oversaw the Microsoft Research unit and the company’s technology-policy relationships with governments such as China and Russia.

Rudder previously served as senior vice president for servers and tools and oversaw Microsoft’s relationship with software developers.