Hold on to your hats, or maybe your patents, because Microsoft just threw a big twist into an intellectual-property saga that has been gripping the mobile industry. And no, we’re not talking about the lost iPhone prototype.

The Redmond company says mobile-phone maker HTC will pay Microsoft an undisclosed sum to license a series of patents that, according to Microsoft, cover technology in HTC mobile phones that use Google's Android operating system. Of course, that would be the same HTC that Apple has sued for patent infringement over the same Google Android devices.

HTC also makes Windows Phones, so it might seem that Microsoft, through the deal, is providing its partner with IP ammunition to use in its defense against Apple, Microsoft’s longtime rival. But that isn't what's happening. Instead, the deal represents Microsoft drawing a line in the sand against its other archrival, Google -- and asserting that Microsoft, like Apple, believes Android infringes on its patents. The HTC deal represents the first in what Microsoft hopes will be a series of patent peace accords with Android device makers.

How do we know this? Here's a statement on the issue from Horacio Gutierrez, Microsoft corporate vice president and deputy general counsel of intellectual property and licensing, with the key part emphasized in bold.

Horacio Gutierrez

"Microsoft has a decades-long record of investment in software platforms. As a result, we have built a significant patent portfolio in this field, and we have a responsibility to our customers, partners, and shareholders to ensure that competitors do not free ride on our innovations. We have also consistently taken a proactive approach to licensing to resolve IP infringement by other companies, and have been talking with several device manufacturers to address our concerns relative to the Android mobile platform."

Microsoft's competitive position has steadily eroded in the mobile phone industry in recent years, losing ground to the iPhone, Android and other competitors, but the HTC deal shows how the Redmond company's big patent portfolio can make it a player even when it doesn’t dominate a market.

HTC is paying unspecified royalties to Microsoft under the deal. Microsoft didn't provide specifics about what HTC licensed, precisely, or how Microsoft believes Android infringes on its patents. Those details are likely to remain murky unless the situation results in a lawsuit, which the Redmond company has generally used only as a last resort in these intellectual-property dealings.

Google, for the record, has spoken out in defense of Android in response to Apple’s patent claims.

The patents that Microsoft has licensed to HTC aren't expected to play a role in the device maker's dispute with Apple over Android devices. However, Microsoft and Apple separately have their own patent cross-licensing agreement -- which means that, because of the interrelated deals, HTC would be protected from any potential claims by Apple that HTC's Windows Phone devices infringe on Apple's patents.

Where is Microsoft headed with this? In a March 16 blog post, Microsoft's Gutierrez made it clear that he expects lots of "activity" in this area over the next few years as the various players in the smart-phone industry wrestle over royalties. "Apple v. HTC was not the beginning of this process, and it isn’t the end of the story either," he wrote at the time.

No doubt Microsoft's newly announced patent agreement with HTC won't be the end of the story, either. But given all the twists so far, where it goes next is anyone’s guess.