Microsoft’s decision to acquire Nokia’s smartphone business in 2013 was one of the company’s greatest failures ever, an all-in bet by CEO Steve Ballmer to unify Windows on the desktop, on tablets, and on mobile phones.

Under the leadership of former Microsoft executive Stephen Elop, Nokia had been Microsoft’s most enthusiastic OEM partner, delivering beautiful Windows Phone hardware that failed to win over consumers.

Windows diehards loved the devices, but they didn’t make of a dent in the market share of the iPhone-Android duopoly.

Rumor has it that the decision to buy Nokia was inspired by the Finnish company’s threat to switch to Android. In retrospect, that might have been a better decision for all concerned. Instead, Microsoft wound up writing off its entire investment in Nokia less than two years later, laying off the workforce and dumping its manufacturing capacity.

Nokia’s noncompete agreement with Microsoft expired in 2016. Today, the company sells a variety of Android-powered devices under the Nokia brand name.