In newly revealed court documents, Microsoft claims that Samsung paid it $1 billion last year under a 2011 patent deal that allowed the South Korean company to make and sell its smartphone and tablets running the Google’s Android operating system.

The documents are from a Microsoft lawsuit filed in federal court in August after Samsung balked at paying $6.9 million in interest from last year, claiming it was not obligated to do so because Microsoft purchased Nokia and thus breached the 2011 pact, according to 9to5Google, which elaborates that Samsung claimed in response to the new lawsuit that the Nokia purchase violated “the cross-licensing patent deal.”

Re/code says the contract calls for Samsung to pay a “royalty for each Android phone and tablet it makes.”

Microsoft has aggressively pursued its intellectual property used in a variety of Android phones since 2011, entering deals with HTC and LG in addition to Samsung – which has acceded to the top of the Android food chain – that reeled Microsoft hundreds of millions of dollars.

The Linux-based Android incorporates many Microsoft patents, and 9to5Google in 2011 cited “pundits” who pointed out the HTC deal alone made Microsoft “more money then licensing fees collected from Windows Phone partners.” The Windows Phone market share stood at a paltry 2.5 percent this year.

Microsoft’s deputy general counsel David Howard said in a statement released Friday that the company was “confident … our case is strong” and it would prevail in the federal lawsuit. He added, “Microsoft values and respects our long partnership with Samsung, is committed to it, and expects it to continue.”