Facebook CEO Mark Zuckerberg considered buying the popular videogame engine Unity back in 2015. The information has come to light thanks to a book titled ‘The History of the Future’, written by Blake Harris, that outlines the events surrounding Facebook’s acquisition of Oculus.

Harris gained access to an email about Zuckerberg’s interest in buying Unity. Within the email, dated June 22 2015, Zuckerberg writes about his hopes of establishing Facebook as a competitor in the VR marketplace. You can read the full 2,500-word email over on TechCrunch.

Zuckerberg goes on to further explain his rationale. “Given the overall opportunity of strengthening our position in the next major wave of computing I think it’s a clear call to do everything we can to increase our chances. A few billion dollars is expensive, but we can afford it.

“We are vulnerable on mobile to Google and Apple because they make major mobile platforms,” Zuckerberg wrote. “Our goal is not only to win in VR / AR, but also to accelerate its arrival. This is part of my rationale for acquiring companies and increasing investment in them sooner rather than waiting until later to derisk them further.”

“If someone else buys Unity or the leader in any core technology component of this new ecosystem, we risk being taken out of the market completely if that acquirer is hostile and decides not to support us.”

Obviously, Zuckerberg’s plans to buy Unity never came to fruition – but it’s interesting to see Facebook’s competitive tenacity in action.