In September 2013, Microsoft announced its intent to acquire Nokia's mobile device business for $7.1 billion, as part of a strategy under CEO Steve Ballmer for Microsoft to be a "devices and services" company. Despite the growth of Windows Phone and the Lumia range (which accounted for nearly 90% of all Windows Phone devices sold), the platform never had significant market share in the key U.S. market, and Microsoft was unable to maintain Windows Phone's momentum in the years that followed, resulting in dwindling interest from users and app developers. After Balmer was succeeded by Satya Nadella (who has placed a larger focus on software and cloud computing) as CEO of Microsoft, it took a $7.6 billion write-off on the Nokia assets in July 2015, and laid off nearly the entire Microsoft Mobile unit in May 2016.