[1][2] On 3 September 2013, Microsoft announced its purchase of Nokia's mobile device business, with the deal closing on 25 April 2014.

A supposed successor called Microsoft Lumia 960 (codenamed Northstar) was reportedly canceled while being in its prototype tests level.

From 1998 to 2012, Nokia was the largest vendor of mobile phones in the world, which included early smartphones built on its Symbian platform.

However, in recent years, its market share declined as a result of the growing use of touchscreen smartphones from other vendors, such as Apple's iPhone line and Android-based products.

In 2010, its market share had declined to 28%, and in April 2012, Samsung Electronics (a prominent user of Android) ultimately overtook Nokia as the largest mobile phone vendor in the world.

[20][21] In February 2011, Stephen Elop and Microsoft's CEO Steve Ballmer jointly announced a major business partnership between Nokia and Microsoft, which would see Nokia adopt Windows Phone as its primary platform on future smartphones, replacing both Symbian and MeeGo.

[25][26] Motivated by requests from the U.S. carrier AT&T for an LTE-enabled device, Nokia quickly developed the Lumia 900 as a follow-up, first unveiled at the 2012 International CES.

[18][27] In early 2012, Nokia released the Lumia 610, a new entry-level device taking advantage of the lower system requirements introduced by Windows Phone 7's "Tango" update.

The Lumia 920 also notably featured Qi wireless charging, and a "PureView" camera with optical image stabilization.

While Nokia received criticism when it was revealed that a demonstration video of its image stabilization technology was, in fact, filmed using a professional camera, the Lumia 920 was a commercial success for the company.

[44] Although sales of the Lumia line had exceeded those of BlackBerry in the same period, Nokia still made an operating loss of €115m, with revenues falling 24% to €5.7bn following the second quarter of 2013.

[45][46] In Q3 2013, Lumia sales hit 8.8 million worldwide; over three times higher than the same period the year before; and double the figure in North America compared to the previous quarter.

[47][48] At the same time, overall Windows Phone market share hit double figures in several countries in Europe and other regions.

[49] On 3 September 2013, Microsoft announced its intent to acquire Nokia's mobile phone business (including rights to the Lumia and low-end Asha brands) in an overall deal of over US$7bn.

Stephen Elop stepped down as Nokia's CEO and returned to Microsoft as its head of devices as part of the deal, which closed in early 2014.

[57] On 13 September 2013, the New York Times writer Nick Wingfield revealed that Nokia had been testing the Android operating system on its Lumia hardware.

[58] It was one of two known Android projects at the company; the other was running the OS on low–end Asha hardware, which resulted in the Nokia X family of devices.

This would reportedly include a write down of approximately US$7.6 billion on the acquisition of Nokia's mobile phone business and a layoff of around 7,200 employees.

[91] Since the Lumia series make up 95% of total Windows Phone/Windows 10 Mobile sales, the operating system market share also shrunk along with it.

[95] However, operating system updates are not subject to these constraints if users are part of Microsoft's Windows Insider or Preview for Developers programs.