Just days after OpenAI showed a bot beating a Dota 2 professional in the summer of 2017, Altman responded to Nadella’s congratulations email with a proposal for a much bigger partnership with OpenAI to fund its next phase of AI research. OpenAI needed large sums of compute to expand the Dota 2 project, far beyond the Azure credits it was using from Microsoft at the time. “Probably something like $300 million at Azure list prices” according to Altman. This initially spooked some executives inside Microsoft.

“For those numbers to make sense we’d have to be generating significant incremental revenue directly due to the deal ($500 million+) that couldn’t be gained in a more efficient way,” said Jason Zander, who was Microsoft’s Azure chief at the time, in an August 2017 email to Nadella.

Altman came back with an alternative proposal several months later to “create a partnership with Xbox around gaming, and an open offer to share their technology and IP in exchange for expanded sponsorship for their Dota research,” according to Brett Tanzer, now VP of Azure solutions and ecosystem. The Xbox team was interested in “exploring collaboration opportunities,” but couldn’t commit to the research costs by itself.

Microsoft CTO Kevin Scott then weighed in on the debate over whether to give OpenAI more Azure credits for its research in an email to Nadella in January 2018. He wasn’t sure what Microsoft was “going to get out of [the deal]” and wasn’t sure how the Dota efforts would benefit the company, but he was definitely concerned about OpenAI moving over to Microsoft’s biggest cloud rival.