Over the last six months, Microsoft has targeted several of Google’s Android partners with patent infringement lawsuits, but has yet to go after Google itself.

The latest example is Microsoft’s campaign against Barnes & Noble, which it says violates Microsoft patents in its Nook e-book reader that runs Android. The company has also sued Foxconn and Inventec, hardware manufacturers that build components for the Nook. The latest lawsuit follows last October’s Microsoft attack on Motorola, another key Google Android partner.

Taken together, these developments suggest that Microsoft is waging a proxy battle against Google by targeting its partners, while holding fire on Google itself, perhaps wary of a full-on Battle Royale with the web-search juggernaut.

But that’s not the case, a Microsoft spokesperson told Wired.com.

“Microsoft has taken these actions against Barnes & Noble, Foxconn and Inventec because they are commercializing products that infringe our patented innovations,” the Microsoft representative said. “In the technology industry, device manufacturers are the point in the chain of commerce at which steps are taken to clear third party patent rights.”

In other words, Microsoft says it is targeting the device makers, not Google itself, because they are the ones bringing infringing products to market.

“The Android platform infringes a number of Microsoft’s patents, and companies shipping Android devices must respect our intellectual property rights,” the spokesperson added.

Still, it’s hard not to see Microsoft’s claims against Google’s Android partners as a roundabout attack on Google. After all, Microsoft appears to be asserting the right to issue patent licenses for one of its competitors’ signature products — and make no mistake, Android may be open-source, but it is very much a Google product.

And Google sees Microsoft’s actions as enough of a threat that it felt compelled to issue a statement objecting to the lawsuit.

“Sweeping software patent claims like Microsoft’s threaten innovation,” Google said. “While we are not a party to this lawsuit, we stand behind the Android platform and the partners who have helped us to develop it.”

Microsoft has been losing market share in the mobile space to Android, as well as Apple’s iPhone.

“Microsoft should focus on innovating,” TechDirt’s Mike Masnick observed. “Not bitching about what competitors are doing better than it did.”

Time will tell whether Microsoft ultimately feels compelled to go after Google itself, or will remain content to target the company’s weaker partners.