Companies sometimes do odd things in response to their competitors, but Google’s $12.5 billion agreement to acquire Motorola ranks up there with some of the most unusual moves we’ve ever seen.

In short, Google is buying one of its major handset partners, while insisting that it will still be able to keep other Android handset makers happy. The companies promise that the combination will put them in a better position to bring innovations to market.

But the underlying motivation was Motorola’s portfolio of more than 17,000 patents, and the protection they promise to Android.

“Our acquisition of Motorola will increase competition by strengthening Google’s patent portfolio, which will enable us to better protect Android from anti-competitive threats from Microsoft, Apple and other companies,” said Larry Page, Google’s CEO, in a post about the deal this morning.

GigaOm reports that Microsoft was also interested in buying Motorola — thereby strengthening Microsoft’s own patent lawsuits against Android. The prospect of that spurred Google into action, grabbing Motorola and its patents for itself, according to the GigaOm report.

Now, Microsoft is seeking to use Google’s Motorola deal as a point of competitive differentiation for Windows Phone.

“Investing in a broad and truly open mobile ecosystem is important for the industry and consumers alike, and Windows Phone is now the only platform that does so with equal opportunity for all partners,”  said Andy Lees, the Windows Phone president, in a statement to AllThingsD today.

Matt Rosoff of Business Insider calls that “nonsense,” citing the preferential treatment that Nokia gets as part of its Microsoft partnership.

Google’s Motorola deal has stirred speculation that Microsoft might buy Nokia or BlackBerry maker RIM in response, but ZDNet’s Mary Jo Foley isn’t buying it. “Microsoft execs have found ways to structure its strategic partnerships so that Redmond gets what it wants from the participants without having to buy companies outright.”

And finally, the award for Prognosticator of the Year has been all but locked up by analyst Ben Bajarin, who published this piece last week: Why Google Should Buy Motorola.

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