Yesterday, in a post ^[1] on Google’s main blog, Google’s SVP and chief legal counsel David Drummond accused Apple and Microsoft of waging an anti-competitive campaign against Android to keep Google from getting access to key patents.

“I have worked in the tech sector for over two decades. Microsoft and Apple have always been at each other’s throats, so when they get into bed together you have to start wondering what’s going on,” he said. Drummond went on to describe what he believes is a “hostile, organized campaign against Android by Microsoft, Oracle, Apple, and other companies, waged through bogus patents.”

Microsoft responded to these attacks last night in the form of two short tweets. First, Microsoft’s general counsel Brad Smith tweeted ^[2], “Google says we bought Novell patents to keep them from Google. Really? We asked them to bid jointly with us. They said no.”

Then, Frank Shaw, Microsoft’s head of communications, posted an image ^[3] of an e-mail conversation between Smith and Kent Walker, SVP and general counsel at Google, which indeed confirms that Google was the one to pull out of the joint bid.

So why is Google so up in arms about patents? According to TechCrunch’s MG Siegler, “Because the Nortel loss was just the beginning.” (In early July, Google lost out on a high-stakes ^[4] Nortel patent auction; a group of Google’s rivals, including Apple and Microsoft, won.)

Siegler says that Google “has nearly $40 billion in cash and cash equivalents to spend. But Apple has almost double that. And if Apple teams up with Microsoft again, they’ll have over $100 billion in buying power. At the end of the day, Google will not be able to out-bid Apple, and they’re running out of options.”

While Drummond says the Department of Justice is investigating the Nortel patent issue, Google hasn’t been faring well in the patent courts otherwise, and the company is still dealing with several patent infringement disputes with big and small companies alike.

Read more from Fortune ^[5].